scale-in pd leader after evict the leader

[3AceShowHand]

What problem does this PR solve?

close #2015

This can help TiCDC be more robust to PD leader change, replication latency does not goes up, since there is always a pd leader to contact for make progress.

What is changed and how it works?

transfer the pd leadership, before scale-in pd leader node.

Check List

Tests

• Manual test (add detailed scripts or steps below)

Code changes

Side effects

Related changes

Release notes:

NONE

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AstroProfundis

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[codecov-commenter]

Codecov Report

Merging #2005 (f97d910) into master (760643a) will decrease coverage by 11.70%.
The diff coverage is 58.82%.

❗ Current head f97d910 differs from pull request most recent head 5dda5cf. Consider uploading reports for the commit 5dda5cf to get more accurate results

@@             Coverage Diff             @@
##           master    #2005       +/-   ##
===========================================
- Coverage   52.61%   40.91%   -11.70%     
===========================================
  Files         308      288       -20     
  Lines       35878    33507     -2371     
===========================================
- Hits        18874    13707     -5167     
- Misses      14785    17988     +3203     
+ Partials     2219     1812      -407     

Flag	Coverage Δ
dm	23.92% <2.94%> (-0.23%)	⬇️
playground	?
unittest	?

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

Impacted Files	Coverage Δ
pkg/cluster/spec/cdc.go	45.96% <0.00%> (-14.28%)	⬇️
pkg/cluster/operation/scale_in.go	51.54% <59.38%> (-2.91%)	⬇️
pkg/cluster/operation/upgrade.go	26.29% <100.00%> (-23.71%)	⬇️
pkg/utils/regexp.go	0.00% <0.00%> (-100.00%)	⬇️
components/dm/ansible/worker.go	0.00% <0.00%> (-100.00%)	⬇️
pkg/utils/freeport.go	0.00% <0.00%> (-77.42%)	⬇️
pkg/meta/err.go	0.00% <0.00%> (-76.19%)	⬇️
pkg/utils/semver.go	8.38% <0.00%> (-76.05%)	⬇️
pkg/cluster/api/error.go	0.00% <0.00%> (-75.00%)	⬇️
pkg/crypto/rand/passwd.go	0.00% <0.00%> (-75.00%)	⬇️
... and 129 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[srstack]

/merge

[ti-chi-bot]

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

Commit hash: c061391