br: restore merge split ranges with small data

[Leavrth]

What problem does this PR solve?

Issue Number: close #53532

Problem Summary:
br restore splits too many regions if there are too many small tables whose data size is less than region size.

What changed and how does it work?

ignore some keys to split less regions

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

[tiprow]

Hi @Leavrth. Thanks for your PR.

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[codecov]

Codecov Report

Attention: Patch coverage is 76.92308% with 12 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-8.3@1a0c3ac). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.3     #53595   +/-   ##
================================================
  Coverage               ?   50.9061%           
================================================
  Files                  ?       1700           
  Lines                  ?     610186           
  Branches               ?          0           
================================================
  Hits                   ?     310622           
  Misses                 ?     276094           
  Partials               ?      23470           

Flag	Coverage Δ
integration	23.0564% <76.9230%> (?)

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

Components	Coverage Δ
dumpling	55.1894% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	48.5225% <0.0000%> (?)

[Leavrth]

stuck by tikv/tikv#17278

[Leavrth]

closed by #55104

[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.

To merge this cherry pick:

1. It must be approved by the approvers firstly.
2. AFTER it has been approved by approvers, please wait for the cherry-pick merging approval from triage owners.

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from leavrth, ensuring that each of them provides their approval before proceeding. For more information see the Code Review Process.

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Needs approval from an approver in each of these files:

• br/OWNERS

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[ti-chi-bot]

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

Test name	Commit	Details	Required	Rerun command
pull-integration-ddl-test	4eab96a	link	true	/test pull-integration-ddl-test
pull-br-integration-test	4eab96a	link	true	/test pull-br-integration-test
pull-mysql-client-test	4eab96a	link	true	/test pull-mysql-client-test
idc-jenkins-ci-tidb/check_dev	f9ba925	link	true	/test check-dev
idc-jenkins-ci-tidb/unit-test	f9ba925	link	true	/test unit-test
idc-jenkins-ci-tidb/build	f9ba925	link	true	/test build

Full PR test history. Your PR dashboard.

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