client: use batch-level runtime trace regions

[bb7133]

What problem does this PR solve?

Issue Number: ref #10965

Cherry-pick #10965 to release-8.5-20260323-v8.5.5. This reduces Go runtime trace region overhead by using a batch-level TSO request send region.

What is changed and how does it work?

This backport changes TSO dispatcher tracing from one pdclient.tsoReqSend region per request to one pdclient.tsoReqSendBatch region per processed batch.

Conflict note: the original master PR also touched client/clients/router/client.go, but that router client path does not exist in this release branch, so that part is not applicable here. The final backport only changes client/tso_dispatcher.go.

Check List

Tests:

• git diff --check origin/release-8.5-20260323-v8.5.5...HEAD
• cd client && go test ./... -run '^$' -count=1
• cd client && go test . -run 'TestTSODispatcherTestSuite/TestBasic' -count=1
• cd client && go test . -run 'TestTSODispatcherTestSuite/TestBatchDelaying' -count=1
• cd client && go test . -run 'TestTSODispatcherTestSuite/TestBatchDelaying' -count=1 -trace /tmp/pdclient-tso-batch-20260323.trace and verified the trace contains pdclient.tsoReqSendBatch

Release note

None

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[ti-chi-bot]

Hi @bb7133. Thanks for your PR.

I'm waiting for a tikv member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[bb7133]

CI update:

Most relevant checks are green:

• statics
• tso-function-test
• chunks (7, Client Integration Test)
• chunks (9, MicroService Integration(!TSO))

The failed run is PD Test / chunks (3, Unit Test(3)), and other shards were cancelled after that. The failure is in server/api TestRegionCPUUsageCompatibility: the test itself passed, but goleak found leftover TSO/etcd retry goroutines after server shutdown. This does not touch the changed path in this backport (client/tso_dispatcher.go), and I could not reproduce it locally:

go test ./server/api -run TestRegionCPUUsageCompatibility -count=1

The PR change is still limited to replacing per-request pdclient.tsoReqSend runtime trace regions with the batch-level pdclient.tsoReqSendBatch region in client/tso_dispatcher.go.

I tried to rerun the failed GitHub Actions jobs, but my token does not have repo admin permission:

run 29467474896 cannot be rerun; Must have admin rights to Repository.

Could a maintainer help rerun the failed jobs?