DNM Support BalaceRegion

[CalvinNeo]

What problem does this PR solve?

Issue Number: Close #xxx

What is changed and how does it work?

Check List

Tests

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

Code changes

• Has the configuration change
• Has HTTP API interfaces changed (Don't forget to add the declarative for the new API)
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tiup:
• Need to cherry-pick to the release branch

Release note

None.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[codecov]

Codecov Report

Attention: Patch coverage is 78.76712% with 31 lines in your changes missing coverage. Please review.

Project coverage is 77.57%. Comparing base (024656b) to head (9bfe8b6).
Report is 47 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8497      +/-   ##
==========================================
+ Coverage   77.31%   77.57%   +0.25%     
==========================================
  Files         472      474       +2     
  Lines       61799    62023     +224     
==========================================
+ Hits        47781    48115     +334     
+ Misses      10441    10362      -79     
+ Partials     3577     3546      -31     

Flag	Coverage Δ
unittests	77.57% <78.76%> (+0.25%)	⬆️

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[ti-chi-bot]

[FORMAT CHECKER NOTIFICATION]

Notice: To remove the do-not-merge/needs-linked-issue label, please provide the linked issue number on one line in the PR body, for example: Issue Number: close #123 or Issue Number: ref #456, multiple issues should use full syntax for each issue and be separated by a comma, like: Issue Number: close #123, ref #456.

_{📖 For more info, you can check the "Linking issues" section in the CONTRIBUTING.md.}

[ti-chi-bot]

@CalvinNeo: 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-realcluster-test	9537d03	link	true	/test pull-integration-realcluster-test
idc-jenkins-ci/build	9537d03	link	true	/test build

Full PR test history. Your PR dashboard.

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