More effective structure to deal with scatter regions operators

## Enhancement Task
Speed up the creation of operators and handling heartbeat


```
1 @ 0xf9670e 0xfa8378 0xfa834f 0xfc72e5 0x20d9db0 0x20d9d88 0x20f2235 0x21756c8 0x2174d9f 0x2174929 0xfcb5e1
# 0xfc72e4 sync.runtime_SemacquireRWMutexR+0x24 /usr/local/go/src/runtime/sema.go:82
# 0x20d9daf sync.(*RWMutex).RLock+0x4f /usr/local/go/src/sync/rwmutex.go:71
# 0x20d9d87 github.com/tikv/pd/pkg/schedule/operator.(*Controller).OperatorCount+0x27 /root/pd/pkg/schedule/operator/operator_controller.go:754
# 0x20f2234 github.com/tikv/pd/pkg/schedule/checker.(*Controller).CheckRegion+0x594 /root/pd/pkg/schedule/checker/checker_controller.go:134
# 0x21756c7 github.com/tikv/pd/pkg/schedule.(*Coordinator).tryAddOperators+0x67 /root/pd/pkg/schedule/coordinator.go:301
# 0x2174d9e github.com/tikv/pd/pkg/schedule.(*Coordinator).checkSuspectRegions+0x5e /root/pd/pkg/schedule/coordinator.go:212
# 0x2174928 github.com/tikv/pd/pkg/schedule.(*Coordinator).PatrolRegions+0x248 /root/pd/pkg/schedule/coordinator.go:170

1 @ 0xf65c10 0xf65429 0xfac069 0x102d99f 0x18df847 0x18df819 0x18df759 0x1fa60e8 0x1fa61c7 0x1fa606b 0x1fa6508 0x20d979c 0x20d610d 0x20d3b0f 0x216cca5 0x216c909 0x22777f3 0x2270959 0x174afb5 0x1b3a5da 0x14c7e83 0x1b3a5c3 0x1b3a7f5 0x1b3a5c3 0x1b3a95c 0x1b3a503 0x174ae95 0x14b20e7 0x14b602c 0x14b036d 0xfcb5e1
# 0x102d99e strings.genSplit+0x7e /usr/local/go/src/strings/strings.go:254
# 0x18df846 strings.SplitN+0xa6 /usr/local/go/src/strings/strings.go:283
# 0x18df818 github.com/coreos/go-semver/semver.(*Version).Set+0x78 /root/.gopath/pkg/mod/github.com/coreos/go-semver@v0.3.0/semver/semver.go:74
# 0x18df758 github.com/coreos/go-semver/semver.NewVersion+0x38 /root/.gopath/pkg/mod/github.com/coreos/go-semver@v0.3.0/semver/semver.go:55
# 0x1fa60e7 github.com/tikv/pd/pkg/versioninfo.ParseVersion+0x47 /root/pd/pkg/versioninfo/versioninfo.go:59
# 0x1fa61c6 github.com/tikv/pd/pkg/versioninfo.MustParseVersion+0x26 /root/pd/pkg/versioninfo/versioninfo.go:68
# 0x1fa606a github.com/tikv/pd/pkg/versioninfo.MinSupportedVersion+0x20a /root/pd/pkg/versioninfo/feature.go:71
# 0x1fa6507 github.com/tikv/pd/pkg/versioninfo.IsFeatureSupported+0x67 /root/pd/pkg/versioninfo/versioninfo.go:89
# 0x20d979b github.com/tikv/pd/pkg/schedule/operator.(*Controller).SendScheduleCommand+0x2bb /root/pd/pkg/schedule/operator/operator_controller.go:713
# 0x20d610c github.com/tikv/pd/pkg/schedule/operator.(*Controller).addOperatorLocked+0xbcc /root/pd/pkg/schedule/operator/operator_controller.go:513
# 0x20d3b0e github.com/tikv/pd/pkg/schedule/operator.(*Controller).AddOperator+0x30e /root/pd/pkg/schedule/operator/operator_controller.go:346
# 0x216cca4 github.com/tikv/pd/pkg/schedule/scatter.(*RegionScatterer).scatterRegions+0x304 /root/pd/pkg/schedule/scatter/region_scatterer.go:252
# 0x216c908 github.com/tikv/pd/pkg/schedule/scatter.(*RegionScatterer).ScatterRegionsByID+0x568 /root/pd/pkg/schedule/scatter/region_scatterer.go:215
# 0x22777f2 github.com/tikv/pd/server.scatterRegions+0x92 /root/pd/server/grpc_service.go:2600
# 0x2270958 github.com/tikv/pd/server.(*GrpcServer).ScatterRegion+0x878 /root/pd/server/grpc_service.go:1971
# 0x174afb4 github.com/pingcap/kvproto/pkg/pdpb._PD_ScatterRegion_Handler.func1+0x74 /root/.gopath/pkg/mod/github.com/pingcap/kvproto@v0.0.0-20231222062942-c0c73f41d0b2/pkg/pdpb/pdpb.pb.go:9984
# 0x1b3a5d9 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainUnaryServer.func5.1+0x79 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:31
# 0x14c7e82 github.com/grpc-ecosystem/go-grpc-prometheus.init.(*ServerMetrics).UnaryServerInterceptor.func3+0x82 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-prometheus@v1.2.0/server_metrics.go:107
# 0x1b3a5c2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainUnaryServer.func5.1+0x62 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:34
# 0x1b3a7f4 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.newUnaryInterceptor.func4+0x1d4 /root/.gopath/pkg/mod/go.etcd.io/etcd@v0.5.0-alpha.5.0.20220915004622-85b640cee793/etcdserver/api/v3rpc/interceptor.go:70
# 0x1b3a5c2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainUnaryServer.func5.1+0x62 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:34
# 0x1b3a95b go.etcd.io/etcd/etcdserver/api/v3rpc.Server.newLogUnaryInterceptor.func3+0xbb /root/.gopath/pkg/mod/go.etcd.io/etcd@v0.5.0-alpha.5.0.20220915004622-85b640cee793/etcdserver/api/v3rpc/interceptor.go:77
# 0x1b3a502 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainUnaryServer.func5+0x182 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:39
# 0x174ae94 github.com/pingcap/kvproto/pkg/pdpb._PD_ScatterRegion_Handler+0x134 /root/.gopath/pkg/mod/github.com/pingcap/kvproto@v0.0.0-20231222062942-c0c73f41d0b2/pkg/pdpb/pdpb.pb.go:9986
# 0x14b20e6 google.golang.org/grpc.(*Server).processUnaryRPC+0xd26 /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1024
# 0x14b602b google.golang.org/grpc.(*Server).handleStream+0x9cb /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1313
# 0x14b036c google.golang.org/grpc.(*Server).serveStreams.func1.1+0x8c /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:722

1 @ 0x27d5769 0x1003366 0x17fc18d 0x17f85bb 0x17f1217 0x17f11bc 0x17f0d77 0x17e8cd3 0x17e7b34 0x17e6ed4 0x21c3eb2 0x21d5045 0x2266b05 0x17490b4 0x1b3a2ba 0x14c7d72 0x1b3a2a3 0x1b3c7ab 0x1b3a1e3 0x14b486c 0x14b5feb 0x14b036d 0xfcb5e1
# 0x27d5768 github.com/tikv/pd/pkg/btree.items[...].find.func1+0x48 /root/pd/pkg/btree/btree_generic.go:219
# 0x1003365 sort.Search+0x45 /usr/local/go/src/sort/search.go:65
# 0x17fc18c github.com/tikv/pd/pkg/btree.items[...].find+0x6c /root/pd/pkg/btree/btree_generic.go:219
# 0x17f85ba github.com/tikv/pd/pkg/btree.(*node[...]).iterate+0x7a /root/pd/pkg/btree/btree_generic.go:750
# 0x17f1216 github.com/tikv/pd/pkg/btree.(*BTreeG[...]).DescendLessOrEqual+0x76 /root/pd/pkg/btree/btree_generic.go:1000
# 0x17f11bb github.com/tikv/pd/pkg/core.(*regionTree).find+0x1b /root/pd/pkg/core/region_tree.go:233
# 0x17f0d76 github.com/tikv/pd/pkg/core.(*regionTree).remove+0x76 /root/pd/pkg/core/region_tree.go:188
# 0x17e8cd2 github.com/tikv/pd/pkg/core.(*RegionsInfo).removeRegionFromSubTreeLocked+0x112 /root/pd/pkg/core/region.go:1170
# 0x17e7b33 github.com/tikv/pd/pkg/core.(*RegionsInfo).UpdateSubTree+0xf3 /root/pd/pkg/core/region.go:1029
# 0x17e6ed3 github.com/tikv/pd/pkg/core.(*RegionsInfo).AtomicCheckAndPutRegion+0x253 /root/pd/pkg/core/region.go:920
# 0x21c3eb1 github.com/tikv/pd/server/cluster.(*RaftCluster).processRegionHeartbeat+0x2b1 /root/pd/server/cluster/cluster.go:1035
# 0x21d5044 github.com/tikv/pd/server/cluster.(*RaftCluster).HandleRegionHeartbeat+0x24 /root/pd/server/cluster/cluster_worker.go:37
# 0x2266b04 github.com/tikv/pd/server.(*GrpcServer).RegionHeartbeat+0xfc4 /root/pd/server/grpc_service.go:1291
# 0x17490b3 github.com/pingcap/kvproto/pkg/pdpb._PD_RegionHeartbeat_Handler+0x93 /root/.gopath/pkg/mod/github.com/pingcap/kvproto@v0.0.0-20231222062942-c0c73f41d0b2/pkg/pdpb/pdpb.pb.go:9766
# 0x1b3a2b9 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8.1+0x79 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:71
# 0x14c7d71 github.com/grpc-ecosystem/go-grpc-prometheus.init.(*ServerMetrics).StreamServerInterceptor.func4+0xd1 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-prometheus@v1.2.0/server_metrics.go:121
# 0x1b3a2a2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8.1+0x62 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:74
# 0x1b3c7aa go.etcd.io/etcd/etcdserver/api/v3rpc.newStreamInterceptor.func1+0x46a /root/.gopath/pkg/mod/go.etcd.io/etcd@v0.5.0-alpha.5.0.20220915004622-85b640cee793/etcdserver/api/v3rpc/interceptor.go:237
# 0x1b3a1e2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8+0x182 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:79
# 0x14b486b google.golang.org/grpc.(*Server).processStreamingRPC+0xd4b /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1244
# 0x14b5fea google.golang.org/grpc.(*Server).handleStream+0x98a /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1317
# 0x14b036c google.golang.org/grpc.(*Server).serveStreams.func1.1+0x8c /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:722

2 @ 0xf9670e 0xfa8378 0xfa834f 0xfc72e5 0x20d8cb1 0x20d8c88 0x20d14bd 0x21d50f8 0x2266b05 0x17490b4 0x1b3a2ba 0x14c7d72 0x1b3a2a3 0x1b3c7ab 0x1b3a1e3 0x14b486c 0x14b5feb 0x14b036d 0xfcb5e1
# 0xfc72e4 sync.runtime_SemacquireRWMutexR+0x24 /usr/local/go/src/runtime/sema.go:82
# 0x20d8cb0 sync.(*RWMutex).RLock+0x50 /usr/local/go/src/sync/rwmutex.go:71
# 0x20d8c87 github.com/tikv/pd/pkg/schedule/operator.(*Controller).GetOperator+0x27 /root/pd/pkg/schedule/operator/operator_controller.go:666
# 0x20d14bc github.com/tikv/pd/pkg/schedule/operator.(*Controller).Dispatch+0x5c /root/pd/pkg/schedule/operator/operator_controller.go:109
# 0x21d50f7 github.com/tikv/pd/server/cluster.(*RaftCluster).HandleRegionHeartbeat+0xd7 /root/pd/server/cluster/cluster_worker.go:44
# 0x2266b04 github.com/tikv/pd/server.(*GrpcServer).RegionHeartbeat+0xfc4 /root/pd/server/grpc_service.go:1291
# 0x17490b3 github.com/pingcap/kvproto/pkg/pdpb._PD_RegionHeartbeat_Handler+0x93 /root/.gopath/pkg/mod/github.com/pingcap/kvproto@v0.0.0-20231222062942-c0c73f41d0b2/pkg/pdpb/pdpb.pb.go:9766
# 0x1b3a2b9 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8.1+0x79 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:71
# 0x14c7d71 github.com/grpc-ecosystem/go-grpc-prometheus.init.(*ServerMetrics).StreamServerInterceptor.func4+0xd1 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-prometheus@v1.2.0/server_metrics.go:121
# 0x1b3a2a2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8.1+0x62 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:74
# 0x1b3c7aa go.etcd.io/etcd/etcdserver/api/v3rpc.newStreamInterceptor.func1+0x46a /root/.gopath/pkg/mod/go.etcd.io/etcd@v0.5.0-alpha.5.0.20220915004622-85b640cee793/etcdserver/api/v3rpc/interceptor.go:237
# 0x1b3a1e2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8+0x182 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:79
# 0x14b486b google.golang.org/grpc.(*Server).processStreamingRPC+0xd4b /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1244
# 0x14b5fea google.golang.org/grpc.(*Server).handleStream+0x98a /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1317
# 0x14b036c google.golang.org/grpc.(*Server).serveStreams.func1.1+0x8c /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:722

0xf9670e 0xfa8378 0xfa834f 0xfc7285 0xfd9d3d 0xfdb251 0xfdb232 0x17e7aac 0x17e6ed4 0x21c3eb2 0x21d5045 0x2266b05 0x17490b4 0x1b3a2ba 0x14c7d72 0x1b3a2a3 0x1b3c7ab 0x1b3a1e3 0x14b486c 0x14b5feb 0x14b036d 0xfcb5e1
# 0xfc7284 sync.runtime_SemacquireMutex+0x24 /usr/local/go/src/runtime/sema.go:77
# 0xfd9d3c sync.(*Mutex).lockSlow+0x15c /usr/local/go/src/sync/mutex.go:171
# 0xfdb250 sync.(*Mutex).Lock+0x30 /usr/local/go/src/sync/mutex.go:90
# 0xfdb231 sync.(*RWMutex).Lock+0x11 /usr/local/go/src/sync/rwmutex.go:147
# 0x17e7aab github.com/tikv/pd/pkg/core.(*RegionsInfo).UpdateSubTree+0x6b /root/pd/pkg/core/region.go:1023
# 0x17e6ed3 github.com/tikv/pd/pkg/core.(*RegionsInfo).AtomicCheckAndPutRegion+0x253 /root/pd/pkg/core/region.go:920
# 0x21c3eb1 github.com/tikv/pd/server/cluster.(*RaftCluster).processRegionHeartbeat+0x2b1 /root/pd/server/cluster/cluster.go:1035
# 0x21d5044 github.com/tikv/pd/server/cluster.(*RaftCluster).HandleRegionHeartbeat+0x24 /root/pd/server/cluster/cluster_worker.go:37
# 0x2266b04 github.com/tikv/pd/server.(*GrpcServer).RegionHeartbeat+0xfc4 /root/pd/server/grpc_service.go:1291
# 0x17490b3 github.com/pingcap/kvproto/pkg/pdpb._PD_RegionHeartbeat_Handler+0x93 /root/.gopath/pkg/mod/github.com/pingcap/kvproto@v0.0.0-20231222062942-c0c73f41d0b2/pkg/pdpb/pdpb.pb.go:9766
# 0x1b3a2b9 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8.1+0x79 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:71
# 0x14c7d71 github.com/grpc-ecosystem/go-grpc-prometheus.init.(*ServerMetrics).StreamServerInterceptor.func4+0xd1 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-prometheus@v1.2.0/server_metrics.go:121
# 0x1b3a2a2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8.1+0x62 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:74
# 0x1b3c7aa go.etcd.io/etcd/etcdserver/api/v3rpc.newStreamInterceptor.func1+0x46a /root/.gopath/pkg/mod/go.etcd.io/etcd@v0.5.0-alpha.5.0.20220915004622-85b640cee793/etcdserver/api/v3rpc/interceptor.go:237
# 0x1b3a1e2 go.etcd.io/etcd/etcdserver/api/v3rpc.Server.ChainStreamServer.func8+0x182 /root/.gopath/pkg/mod/github.com/grpc-ecosystem/go-grpc-middleware@v1.0.1-0.20190118093823-f849b5445de4/chain.go:79
# 0x14b486b google.golang.org/grpc.(*Server).processStreamingRPC+0xd4b /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1244
# 0x14b5fea google.golang.org/grpc.(*Server).handleStream+0x98a /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:1317
# 0x14b036c google.golang.org/grpc.(*Server).serveStreams.func1.1+0x8c /root/.gopath/pkg/mod/google.golang.org/grpc@v1.26.0/server.go:722

```