Fix single-replica partition blocking forever during bootstrap/deactivation/disconnection

[justinlin-linkedin]

Summary

When a partition has only one replica, there are no peers, so updateReplicaLagAndCheckSyncStatus is never called by the replication manager. This caused waitBootstrapCompleted (and the equivalent wait methods for deactivation/disconnection) to block forever.

Two changes fix this:

1. Cap catchupTarget at the total number of available peers so hasSyncedUpWithEnoughPeers() returns true when there are zero peers.
2. Check isSyncUpComplete() right after initiation and immediately complete the operation if already satisfied, since no replication events will ever arrive to trigger completion.

Testing Done

Added new unit tests

[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.81%. Comparing base (52ba813) to head (6fcb45d).
⚠️ Report is 348 commits behind head on master.

Files with missing lines	Patch %	Lines
...ub/ambry/clustermap/AmbryReplicaSyncUpManager.java	86.66%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3204      +/-   ##
============================================
+ Coverage     64.24%   69.81%   +5.56%     
- Complexity    10398    12816    +2418     
============================================
  Files           840      930      +90     
  Lines         71755    79101    +7346     
  Branches       8611     9464     +853     
============================================
+ Hits          46099    55222    +9123     
+ Misses        23004    20931    -2073     
- Partials       2652     2948     +296     

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