*: cherry-pick the etcd client health checker improvements

[JmPotato]

What problem does this PR solve?

Issue Number: close #7251, #6291, #7226. Cherry-pick part of code from #7725. #7727, #7743, #7737 and #7779.

What is changed and how does it work?

Cherry-pick the etcd client health checker improvements from #7725. #7727, #7743,  #7737 and #7779.

Check List

Tests

• Unit test
• Integration test
• Manual test

Release note

Enhance PD availability in the event of IO hang causing node unavailability.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• HuSharp
• rleungx

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[HuSharp]

update metrics json as well?

[JmPotato]

update metrics json as well?

Dashboard JSON could be imported or modified manually, so cherry-picking is not that necessary. I prefer to avoid making too many changes in this PR.

[codecov]

Codecov Report

Merging #7793 (1484980) into release-7.5 (ae19047) will increase coverage by 0.06%.
The diff coverage is 85.55%.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-7.5    #7793      +/-   ##
===============================================
+ Coverage        74.53%   74.60%   +0.06%     
===============================================
  Files              443      444       +1     
  Lines            47983    48120     +137     
===============================================
+ Hits             35764    35899     +135     
- Misses            9035     9043       +8     
+ Partials          3184     3178       -6     

Flag	Coverage Δ
unittests	74.60% <85.55%> (+0.06%)	⬆️

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

[HuSharp]

LGTM!

[JmPotato]

/hold

[JmPotato]

/unhold

[JmPotato]

/merge

[ti-chi-bot]

@JmPotato: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

@JmPotato: /merge in this pull request requires 2 approval(s).

In response to this:

/merge

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[JmPotato]

/merge

[ti-chi-bot]

@JmPotato: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

If you have any questions about the PR merge process, please refer to pr process.

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 ti-community-infra/tichi repository.

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 1484980