kv,rpc: adopt static labels

# Metric Refactoring for Static Labels

This issue tracks the migration of existing metrics to use the new static labels feature[^1]. This will help reduce metric cardinality and improve queryability.

[^1]: https://docs.google.com/document/d/1fn5KX0uPUCw1uW4KkCvmP9-svga0F6XSvhnqdg24MpE/edit?tab=t.0#heading=h.9ndo02nsmu

I'm particularly bullish on the first three because it'll be so much easier (on DD) to add one metric and to get to see all the flavors of requests.

Some of the others might be useful as well. I prepared the below using Cursor/Gemini2.5-pro by pointing it at metrics.html and giving it a .txt version of the static labels feature doc.

## DistSender

- [ ] `distsender.rpc.sent`: `method=(addsstable,adminchangereplicas,adminmerge,adminrelocaterange,adminscatter,adminsplit,admintransferlease,adminunsplit,adminverifyprotectedtimestamp,barrier,checkconsistency,clearrange,computechecksum,conditionalput,delete,deleterange,endtxn,excise,export,flushlocktable,gc,get,heartbeattxn,increment,initput,isspanempty,leaseinfo,linkexternalsstable,merge,migrate,probe,pushtxn,put,queryintent,querylocks,queryresolvedtimestamp,querytxn,rangestats,recomputestats,recovertxn,refresh,refreshrange,requestlease,resolveintent,resolveintentrange,reversescan,revertrange,scan,subsume,transferlease,truncatelog,writebatch)`
- [ ] `distsender.rpc.errors`: `error=(ambiguousresulterrtype,batchtimestampbeforegcerrtype,communicationerrtype,conditionfailederrtype,errordetailtype(0),errordetailtype(15),errordetailtype(19),errordetailtype(20),errordetailtype(21),errordetailtype(23),errordetailtype(24),errordetailtype(29),errordetailtype(30),errordetailtype(33),indeterminatecommiterrtype,integeroverflowerrtype,intentmissingerrtype,internalerrtype,invalidleaseerrtype,leaserejectederrtype,lockconflicterrtype,mergeinprogresserrtype,mintimestampboundunsatisfiableerrtype,mvcchistorymutationerrtype,nodeunavailableerrtype,notleaseholdererrtype,oprequirestxnerrtype,optimisticevalconflictserrtype,proxyfailederrtype,raftgroupdeletederrtype,rangefeedretryerrtype,rangekeymismatcherrtype,rangenotfounderrtype,readwithinuncertaintyintervalerrtype,refreshfailederrtype,replicacorruptionerrtype,replicatooolderrtype,replicaunavailableerrtype,storenotfounderrtype,transactionabortederrtype,transactionpusherrtype,transactionretryerrtype,transactionretrywithprotorefresherrtype,transactionstatuserrtype,txnalreadyencounterederrtype,unsupportedrequesterrtype,writeintenterrtype,writetooolderrtype)`

## RPC

- [ ] `rpc.requests_received`: `method=(addsstable,adminchangereplicas,adminmerge,adminrelocaterange,adminscatter,adminsplit,admintransferlease,adminunsplit,adminverifyprotectedtimestamp,barrier,checkconsistency,clearrange,computechecksum,conditionalput,delete,deleterange,endtxn,excise,export,flushlocktable,gc,get,heartbeattxn,increment,initput,isspanempty,leaseinfo,linkexternalsstable,merge,migrate,probe,pushtxn,put,queryintent,querylocks,queryresolvedtimestamp,querytxn,rangestats,recomputestats,recovertxn,refresh,refreshrange,requestlease,resolveintent,resolveintentrange,reversescan,revertrange,scan,subsume,transferlease,truncatelog,writebatch)`

## Raft

- [ ] `raft.rcvd.messages`: `type=(app,appresp,defortifyleader,dropped,fortifyleader,fortifyleaderresp,heartbeat,heartbeatresp,prevote,prevoteresp,prop,snap,timeoutnow,transferleader,vote,voteresp)`

## Admission Control

- [ ] `admission.requests`: `status=(admitted,errored,requested)` `workload=(elastic-cpu,elastic-stores,kv,kv-stores,sql-kv-response,sql-sql-response)` `priority=(bulk-normal-pri,normal-pri,bulk-low-pri,high-pri,locking-normal-pri,user-high-pri,none)`
- [ ] `admission.wait_duration`: `workload=(elastic-cpu,elastic-stores,kv,kv-stores,snapshot_ingest,sql-kv-response,sql-sql-response)` `priority=(bulk-normal-pri,normal-pri,bulk-low-pri,high-pri,locking-normal-pri,user-high-pri,none)`
- [ ] `admission.wait_queue_length`: `workload=(elastic-cpu,elastic-stores,kv,kv-stores,sql-kv-response,sql-sql-response)` `priority=(bulk-normal-pri,normal-pri,bulk-low-pri,high-pri,locking-normal-pri,user-high-pri,none)`

## Allocator

- [ ] `kv.allocator.load_based_lease_transfers`: `reason=(cannot_find_better_candidate,delta_not_significant,existing_not_overfull,follow_the_workload,missing_stats_for_existing_stores,should_transfer)`
- [ ] `kv.allocator.load_based_replica_rebalancing`: `reason=(cannot_find_better_candidate,delta_not_significant,existing_not_overfull,missing_stats_for_existing_store,should_transfer)`

## KV Prober

- [ ] `kv.prober.attempts`: `operation=(planning,read,write)`
- [ ] `kv.prober.failures`: `operation=(planning,read,write)`
- [ ] `kv.prober.latency`: `operation=(read,write)`

## Transactions

- [ ] `txnrecovery.successes`: `outcome=(aborted,committed,pending)`

## Snapshots

- [ ] `range.snapshots.applied`: `type=(initial,non-voter,voter)`
- [ ] `range.snapshots.sent.bytes`: `reason=(total,cross-region,cross-zone,rebalancing,recovery,unknown,upreplication)`
- [ ] `range.snapshots.rcvd.bytes`: `reason=(total,cross-region,cross-zone,rebalancing,recovery,unknown,upreplication)`

## Queues

- [ ] `queue.replicate.removals`: `reason=(dead,decommissioning,learner,rebalance)` `type=(any,nonvoter,voter)`

Jira issue: CRDB-52738