store: remove stores that have no region before balance

[xzhangxian1008]

What problem does this PR solve?

Issue Number: ref #52313

Problem Summary:

What changed and how does it work?

Check List

Tests

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

  • I checked and no code files have been changed.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

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[xzhangxian1008]

/cc @windtalker

[ti-chi-bot]

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[tiprow]

Hi @xzhangxian1008. Thanks for your PR.

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[ti-chi-bot]

@xzhangxian1008: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/check_dev	27b7763	link	true	/test check-dev

Full PR test history. Your PR dashboard.

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[codecov]

Codecov Report

Attention: Patch coverage is 73.91304% with 12 lines in your changes are missing coverage. Please review.

❗ No coverage uploaded for pull request base (release-7.5@2ecc47d). Click here to learn what that means.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #52966   +/-   ##
================================================
  Coverage               ?   72.0010%           
================================================
  Files                  ?       1410           
  Lines                  ?     409511           
  Branches               ?          0           
================================================
  Hits                   ?     294852           
  Misses                 ?      94832           
  Partials               ?      19827           

Flag	Coverage Δ
unit	72.0010% <73.9130%> (?)

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

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.3572% <0.0000%> (?)