ratelimit: support modify BBR config by API

[CabinfeverB]

What problem does this PR solve?

Issue Number: ref #7167

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[bot]]

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[ti-chi-bot[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[bot]]

PR needs rebase.

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.31148% with 9 lines in your changes missing coverage. Please review.

Project coverage is 73.53%. Comparing base (1772ad0) to head (34b6821). Report is 314 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7291      +/-   ##
==========================================
+ Coverage   73.45%   73.53%   +0.07%     
==========================================
  Files         432      433       +1     
  Lines       47886    48123     +237     
==========================================
+ Hits        35175    35387     +212     
- Misses       9667     9683      +16     
- Partials     3044     3053       +9     

Flag	Coverage Δ
unittests	73.53% <96.31%> (+0.07%)	:arrow_up:

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[ti-chi-bot[bot]]

PR needs rebase.

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 kubernetes/test-infra repository.