DATA RACE github.com/tikv/client-go/v2/internal/unionstore/rbt.(*RBT)

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

### 2. What did you expect to see? (Required)

### 3. What did you see instead (Required)

```
==================
WARNING: DATA RACE
Read at 0x00c00833a831 by goroutine 15338:
github.com/tikv/client-go/v2/internal/unionstore/rbt.(*RBT).Dirty()
external/com_github_tikv_client_go_v2/internal/unionstore/rbt/rbt.go:310 +0x57
github.com/tikv/client-go/v2/internal/unionstore.(*rbtDBWithContext).Dirty()
:1 +0x17
github.com/tikv/client-go/v2/txnkv/transaction.(*KVTxn).IsReadOnly()
external/com_github_tikv_client_go_v2/txnkv/transaction/txn.go:1676 +0x5e
github.com/pingcap/tidb/pkg/store/driver/txn.(*tikvTxn).IsReadOnly()
:1 +0x3e
github.com/pingcap/tidb/pkg/session.(*LazyTxn).IsReadOnly()
:1 +0x46
github.com/pingcap/tidb/pkg/executor.(*PointGetExecutor).get()
pkg/executor/point_get.go:636 +0xe3
github.com/pingcap/tidb/pkg/executor.(*PointGetExecutor).getAndLock()
pkg/executor/point_get.go:549 +0x2c4
github.com/pingcap/tidb/pkg/executor.(*PointGetExecutor).Next()
pkg/executor/point_get.go:382 +0x1136
github.com/pingcap/tidb/pkg/executor/internal/exec.Next()
pkg/executor/internal/exec/executor.go:451 +0x418
github.com/pingcap/tidb/pkg/executor.(*SelectLockExec).Next()
pkg/executor/executor.go:1190 +0xde
github.com/pingcap/tidb/pkg/executor/internal/exec.Next()
pkg/executor/internal/exec/executor.go:451 +0x418
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).resultPuller()
pkg/executor/unionexec/union.go:164 +0x969
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).initialize.func1()
pkg/executor/unionexec/union.go:117 +0x5d
Previous write at 0x00c00833a831 by goroutine 15337:
github.com/tikv/client-go/v2/internal/unionstore/rbt.(*RBT).Set()
external/com_github_tikv_client_go_v2/internal/unionstore/rbt/rbt.go:344 +0x2b1
github.com/tikv/client-go/v2/internal/unionstore.(*rbtDBWithContext).set()
external/com_github_tikv_client_go_v2/internal/unionstore/memdb_rbt.go:54 +0x16e
github.com/tikv/client-go/v2/internal/unionstore.(*rbtDBWithContext).UpdateFlags()
external/com_github_tikv_client_go_v2/internal/unionstore/memdb_rbt.go:59 +0x94
github.com/tikv/client-go/v2/txnkv/transaction.(*KVTxn).lockKeys()
external/com_github_tikv_client_go_v2/txnkv/transaction/txn.go:1524 +0x2aa2
github.com/tikv/client-go/v2/txnkv/transaction.(*KVTxn).LockKeysFunc()
external/com_github_tikv_client_go_v2/txnkv/transaction/txn.go:1207 +0x1c6
github.com/pingcap/tidb/pkg/store/driver/txn.(*tikvTxn).LockKeysFunc()
pkg/store/driver/txn/txn_driver.go:106 +0x174
github.com/pingcap/tidb/pkg/session.(*LazyTxn).LockKeysFunc()
pkg/session/txn.go:497 +0x377
github.com/pingcap/tidb/pkg/session.(*LazyTxn).LockKeys()
pkg/session/txn.go:472 +0x84
github.com/pingcap/tidb/pkg/executor.doLockKeys()
pkg/executor/executor.go:1312 +0x30c
github.com/pingcap/tidb/pkg/executor.(*SelectLockExec).Next()
pkg/executor/executor.go:1241 +0x82e
github.com/pingcap/tidb/pkg/executor/internal/exec.Next()
pkg/executor/internal/exec/executor.go:451 +0x418
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).resultPuller()
pkg/executor/unionexec/union.go:164 +0x969
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).initialize.func1()
pkg/executor/unionexec/union.go:117 +0x5d
Goroutine 15338 (running) created at:
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).initialize()
pkg/executor/unionexec/union.go:117 +0x52a
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).Next()
pkg/executor/unionexec/union.go:190 +0xb7
github.com/pingcap/tidb/pkg/executor/internal/exec.Next()
pkg/executor/internal/exec/executor.go:451 +0x418
github.com/pingcap/tidb/pkg/executor/aggregate.(*HashAggExec).fetchChildData()
pkg/executor/aggregate/agg_hash_executor.go:482 +0x2b8
github.com/pingcap/tidb/pkg/executor/aggregate.(*HashAggExec).prepare4ParallelExec.func3()
pkg/executor/aggregate/agg_hash_executor.go:561 +0x5d
Goroutine 15337 (finished) created at:
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).initialize()
pkg/executor/unionexec/union.go:117 +0x52a
github.com/pingcap/tidb/pkg/executor/unionexec.(*UnionExec).Next()
pkg/executor/unionexec/union.go:190 +0xb7
github.com/pingcap/tidb/pkg/executor/internal/exec.Next()
pkg/executor/internal/exec/executor.go:451 +0x418
github.com/pingcap/tidb/pkg/executor/aggregate.(*HashAggExec).fetchChildData()
pkg/executor/aggregate/agg_hash_executor.go:482 +0x2b8
github.com/pingcap/tidb/pkg/executor/aggregate.(*HashAggExec).prepare4ParallelExec.func3()
pkg/executor/aggregate/agg_hash_executor.go:561 +0x5d
==================
```
### 4. What is your TiDB version? (Required)