checker: fix the too many orphan peers cannot be removed (#6574)

[ti-chi-bot]

This is an automated cherry-pick of #6574

What problem does this PR solve?

Issue Number: Close #6573

What is changed and how does it work?

rule-checker: fix the too many orphan peers that cannot be removed
- let the health peer can be removed once there exist redundant

Check List

Tests

• Unit test

Release note

Fix the issue too many peers/learners cannot be removed

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CabinfeverB
• lhy1024

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[nolouch]

PTAL @rleungx @CabinfeverB

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.08 🎉

Comparison is base (9d320ef) 75.64% compared to head (7bf17e0) 75.72%.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-6.5    #6575      +/-   ##
===============================================
+ Coverage        75.64%   75.72%   +0.08%     
===============================================
  Files              330      330              
  Lines            33113    33118       +5     
===============================================
+ Hits             25047    25080      +33     
+ Misses            5911     5893      -18     
+ Partials          2155     2145      -10     

Flag	Coverage Δ
unittests	75.72% <100.00%> (+0.08%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/schedule/checker/rule_checker.go	83.45% <100.00%> (+2.13%)	⬆️

... and 27 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[nolouch]

/merge

[ti-chi-bot]

@nolouch: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

If you have any questions about the PR merge process, please refer to pr process.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 7bf17e0