fix data race of LocalAdmissionController (#10332)

[ti-chi-bot]

This is an automated cherry-pick of #10332

What problem does this PR solve?

Issue Number: close #10331

Problem Summary:

What is changed and how it works?

1. fix data race of keyspace_resource_groups
2. refine the logic of handling current_tick/cur_tick_end.
3. add endRequest when got error in the logic of handling GAC resp. Otherwise this rg will enter degrade mode, and it will not acquire any tokens from GAC for DEGRADE_MODE_DURATION seconds (120s)

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

fix data race of LocalAdmissionController

[ti-chi-bot]

@guo-shaoge This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[ti-chi-bot]

@ti-chi-bot: ## If you want to know how to resolve it, please read the guide in TiDB Dev Guide.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: solotzg, wshwsh12

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• OWNERS [solotzg,wshwsh12]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-08-13 06:26:23.333918809 +0000 UTC m=+421582.368502038: ☑️ agreed by wshwsh12.
• 2025-08-13 06:26:54.397252533 +0000 UTC m=+421613.431835761: ☑️ agreed by solotzg.

[guo-shaoge]

this pr has been tagged as next version in tirelease, and should be merged in next version.