Fix AddConfigNode retry idempotency

[CRZbulabula]

Summary

This PR makes ConfigNode membership changes idempotent during AddConfigNodeProcedure retry paths.

When ADD_CONSENSUS_GROUP times out, the first request may have already created the local ConfigRegion peer on the joining ConfigNode. A retry then sees the consensus group already exists and previously failed the procedure, which could leave the new ConfigNode process alive but not registered in the cluster.

Changes:

• Treat ConsensusGroupAlreadyExistException from createLocalPeer as success.
• Treat PeerAlreadyInConsensusGroupException from addRemotePeer as success.
• Treat PeerNotInConsensusGroupException from rollback removeRemotePeer as success.
• Allow deleteConfigNodePeer to clean up a local peer even before the ConfigNode is present in registeredConfigNodes, while still rejecting requests targeting a different ConfigNode id.

Tests

mvn spotless:apply -pl iotdb-core/confignode
mvn test -pl iotdb-core/confignode -Dtest=ConsensusManagerTest,ConfigNodeRPCServiceProcessorTest

Both commands passed. The local sandbox logs Develocity cache/write warnings for ~/.m2/.develocity, but Maven reports BUILD SUCCESS.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.86%. Comparing base (3d98ea5) to head (8a2485a).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...confignode/manager/consensus/ConsensusManager.java	86.66%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #17874      +/-   ##
============================================
+ Coverage     40.85%   40.86%   +0.01%     
  Complexity     2611     2611              
============================================
  Files          5201     5201              
  Lines        354010   354028      +18     
  Branches      45313    45314       +1     
============================================
+ Hits         144626   144679      +53     
+ Misses       209384   209349      -35     

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