resource_control: delete metric children by creation-time keyspace_name

[mvanhorn]

What problem does this PR solve?

Issue Number: Closes #10871

Resource Control metric caches in the resource manager are keyed by keyspace ID, resource group and RU type, but the underlying Prometheus children are created and removed by their label values, which include keyspace_name. When a metric child is first created while the keyspace-name cache misses, it carries a fallback label such as keyspace-123. Later, the periodic cleanup loop resolves the real keyspace name (for example tenant-a) from storage and calls DeleteLabelValues with that real name. Because creation used keyspace-123 but deletion uses tenant-a, the original child is never removed and leaks as a stale Prometheus series, leaving duplicated curves in Grafana for the same keyspace.

What is changed and how does it work?

The cached counter, gauge and max-per-sec tracker entries now remember the keyspace_name label string actually used when each child was created, and cleanup deletes by that recorded value rather than a freshly resolved one. This keeps the create and delete label values symmetric so no orphaned child remains:

• counterMetrics and gaugeMetrics store the creation-time keyspaceName; deleteMetrics uses the cached value (falling back to the passed-in name only when no cache entry exists).
• deleteMaxPerSecTracker removes the max-per-sec gauge children using the tracker's stored keyspaceName; those two deletions move out of the shared deleteLabelValues helper so they always use the creation-time value.
• gaugeMetrics.setGroup deletes override-settings children by the struct's stored keyspaceName.

This mirrors the principle already applied to the request metrics in #10867.

resource_control: delete metric children by creation-time keyspace_name

Check List

Tests

• Unit test

Code changes

• No configuration, API, or persistent data change

Side effects

• None

Release note

Fix a Resource Control metrics leak where Prometheus series created with a fallback keyspace_name label were not removed during cleanup.

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[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.20%. Comparing base (5eb3dab) to head (7f9be67).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #10910      +/-   ##
==========================================
+ Coverage   79.06%   79.20%   +0.14%     
==========================================
  Files         540      540              
  Lines       74535    74672     +137     
==========================================
+ Hits        58929    59142     +213     
+ Misses      11423    11356      -67     
+ Partials     4183     4174       -9     

Flag	Coverage Δ
unittests	79.20% <91.66%> (+0.14%)	⬆️

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[rleungx]

Please fix CI, the rest LGTM.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rleungx

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-06-18 08:18:33.202550501 +0000 UTC m=+1639214.272867891: ☑️ agreed by rleungx.

[rleungx]

/ok-to-test