core: region heartbeat with bucket meta

[bufferflies]

What problem does this PR solve?

Issue Number: Close #10117

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]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[ti-chi-bot]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.43%. Comparing base (6bfdb20) to head (bd6a2a2).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #10120   +/-   ##
=======================================
  Coverage   78.42%   78.43%           
=======================================
  Files         518      518           
  Lines       69493    69407   -86     
=======================================
- Hits        54503    54442   -61     
+ Misses      11042    11024   -18     
+ Partials     3948     3941    -7     

Flag	Coverage Δ
unittests	78.43% <100.00%> (+<0.01%)	⬆️

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[ti-chi-bot]

@bufferflies: 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
pull-unit-test-next-gen-3	bd6a2a2	link	true	/test pull-unit-test-next-gen-3

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[rleungx]

If we use SetBucketMeta, do we still need UpdateBuckets?