Improve ReplaceMemberRollback UT

[yuwmao]

• Add flip to control complete_replace_member, it is enabled after we check replace member intermediate status.
• In ReplaceMemberRollback UT, wait for in member being caught up before rollback.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.37%. Comparing base (1a0cef8) to head (faed0d2).
⚠️ Report is 305 commits behind head on master.

Files with missing lines	Patch %	Lines
src/lib/replication/service/raft_repl_service.cpp	50.00%	1 Missing and 1 partial ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #844      +/-   ##
==========================================
- Coverage   56.51%   49.37%   -7.15%     
==========================================
  Files         108      110       +2     
  Lines       10300    11460    +1160     
  Branches     1402     5431    +4029     
==========================================
- Hits         5821     5658     -163     
+ Misses       3894     2099    -1795     
- Partials      585     3703    +3118     

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[JacksonYao287]

LGTM , except one minor comment.

on question, is this a temporary solution to unblock UT now? or this will be a final solution, which means we will never involve monitor_replace_member_replication_status in raft_repl_dev UT?

[yuwmao]

LGTM , except one minor comment.

on question, is this a temporary solution to unblock UT now? or this will be a final solution, which means we will never involve monitor_replace_member_replication_status in raft_repl_dev UT?

Actually monitor_replace_member_replication_status is still involved(still rely on it to complete). After removing flip at L75, the monitor_replace_member_replication_status is restored which will trigger complete_replace_member. The purpose of this flip is to skip monitor_replace_member_replication_status before we verify the check_replace_member_status to guarantees complete_replace_member happens after the check.
The reason why I don't manually call monitor_replace_member_replication_status once to trigger complete is because complete_replace_member may fail, periodical monitor_replace_member_replication_status supports retry.