client/http: handle 503/leader/primary change to schedule member check

[JmPotato]

What problem does this PR solve?

Issue Number: ref #8142, ref #7300.

What is changed and how does it work?

- Schedule a member change check when the HTTP status code is 503 or receives a leader/primary change error.
- Only return the latest error in backoffer to ensure the logic of successful retry.

Check List

Tests

• Unit test
• Integration test

Release note

None.

[ti-chi-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 95.12195% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 77.27%. Comparing base (c498063) to head (d952e06).

❗ Current head d952e06 differs from pull request most recent head 541981c

Please upload reports for the commit 541981c to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8223      +/-   ##
==========================================
+ Coverage   77.25%   77.27%   +0.02%     
==========================================
  Files         471      471              
  Lines       61339    61361      +22     
==========================================
+ Hits        47385    47418      +33     
+ Misses      10382    10376       -6     
+ Partials     3572     3567       -5     

Flag	Coverage Δ
unittests	77.27% <95.12%> (+0.02%)	⬆️

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[JmPotato]

/hold

[JmPotato]

/unhold

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