affinity: use isRegionPlacementRuleSatisfiedWithBestLocation instead of IsRegionReplicated (#10192)

[ti-chi-bot]

This is an automated cherry-pick of #10192

What problem does this PR solve?

Issue Number: Ref #10149

What is changed and how does it work?

check location labels in AffinityChecker

Check List

Tests

• Unit test

Related changes

• Need to cherry-pick to the release branch

Release note

None.

Summary by CodeRabbit

• New Features

  • Affinity checks now evaluate placement-rule satisfaction (including a cached and cacheless region fit path) and region label isolation reports a numeric level for level-based checks.

• Bug Fixes

  • Better detection and handling of superior replica placements, stricter enforcement of isolation constraints, preservation of learners, and early exit when placement rules are disabled.

• Metrics

  • Added a counter for placement-rules-disabled occurrences.

• Tests

  • Expanded and updated tests for placement-rule, isolation-level, normalization, and placement interactions.

[ti-chi-bot]

@HunDunDM 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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[lhy1024]

@HunDunDM please fix conflict

[HunDunDM]

We also need to cherry-pick #9439 and #9512 .

[HunDunDM]

/cherry-pick-invite

[ti-chi-bot]

@HunDunDM Please accept the invitation then you can push to the cherry-pick pull requests.
Comment with "/cherry-pick-invite" if the invitation is expired.
https://github.com/ti-chi-bot/pd/invitations

[HunDunDM]

/unhold

[codecov]

Codecov Report

❌ Patch coverage is 90.78014% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.08%. Comparing base (d76bec1) to head (0d6ceb4).
⚠️ Report is 16 commits behind head on release-8.5.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-8.5   #10741      +/-   ##
===============================================
+ Coverage        77.93%   78.08%   +0.15%     
===============================================
  Files              484      488       +4     
  Lines            65594    66959    +1365     
===============================================
+ Hits             51119    52288    +1169     
- Misses           10703    10827     +124     
- Partials          3772     3844      +72     

Flag	Coverage Δ
unittests	78.08% <90.78%> (+0.15%)	⬆️

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[lhy1024]

@rleungx PTAL

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lhy1024, rleungx

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Needs approval from an approver in each of these files:

• OWNERS [lhy1024,rleungx]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-06-04 03:36:38.787210355 +0000 UTC m=+412699.857527745: ☑️ agreed by lhy1024.
• 2026-06-04 10:24:18.641670273 +0000 UTC m=+437159.711987673: ☑️ agreed by rleungx.