Fix region migration reliability regressions

[Pengzna]

Summary

• avoid double retry storms when deleting old region peers on DataNodes that are already Unknown
• allow IoTConsensus createLocalPeer to reuse an existing consensus directory after cluster crash recovery
• assign IoTConsensusV2 realtime replicate indexes lazily when events are actually supplied so HybridSource cannot create holes

Validation

• mvn -Dtest=RegionMaintainHandlerConsensusPipeTest -DskipITs -DfailIfNoTests=false -Dsurefire.failIfNoSpecifiedTests=false -ntp test
• mvn -Dtest=StabilityTest#createLocalPeerShouldAllowExistingConsensusDir -DskipITs -DfailIfNoTests=false -Dsurefire.failIfNoSpecifiedTests=false -ntp test
• mvn -pl iotdb-core/datanode -am -Dtest=PipeRealtimeReplicateIndexAssignmentTest -DskipITs -DfailIfNoTests=false -Dsurefire.failIfNoSpecifiedTests=false -ntp test
• mvn verify -pl integration-test -am -P with-integration-tests,DailyIT -DskipUTs -DintegrationTest.forkCount=1 -DConfigNodeMaxHeapSize=256 -DDataNodeMaxHeapSize=1024 -DDataNodeMaxDirectMemorySize=768 -Dit.test=IoTDBRegionMigrateOriginalCrashWhenDeleteLocalPeerForIoTV1IT#crashAfterDelete -Dfailsafe.failIfNoSpecifiedTests=false -Dsurefire.failIfNoSpecifiedTests=false -ntp
• mvn verify -pl integration-test -am -P with-integration-tests,DailyIT -DskipUTs -DintegrationTest.forkCount=1 -DConfigNodeMaxHeapSize=256 -DDataNodeMaxHeapSize=1024 -DDataNodeMaxDirectMemorySize=768 -Dit.test=IoTDBIoTConsensusV2Stream3C3DBasicIT#testDeleteTimeSeriesReplicaConsistency -Dfailsafe.failIfNoSpecifiedTests=false -Dsurefire.failIfNoSpecifiedTests=false -ntp
• mvn verify -pl integration-test -am -P with-integration-tests,DailyIT -DskipUTs -DintegrationTest.forkCount=1 -DConfigNodeMaxHeapSize=256 -DDataNodeMaxHeapSize=1024 -DDataNodeMaxDirectMemorySize=768 -Dit.test=IoTDBRegionMigrateOriginalCrashWhenDeleteLocalPeerForIoTV2BatchIT,IoTDBRegionMigrateOriginalCrashWhenDeleteLocalPeerForIoTV2StreamIT,IoTDBRegionMigrateClusterCrashIoTV1IT#clusterCrash1,IoTDBIoTConsensusV2Batch3C3DBasicIT#testDeleteTimeSeriesReplicaConsistency -Dfailsafe.failIfNoSpecifiedTests=false -Dsurefire.failIfNoSpecifiedTests=false -ntp

[Copilot]

Pull request overview

This PR addresses region migration reliability regressions across ConfigNode region-maintenance RPC behavior, IoTConsensus crash-recovery peer creation, and IoTConsensusV2 realtime replication index assignment in the Pipe subsystem.

Changes:

• Avoid “double retry storms” by using a single RPC attempt for DELETE_OLD_REGION_PEER when the target DataNode is Unknown.
• Allow IoTConsensus#createLocalPeer to proceed when the consensus peer directory already exists (e.g., crash recovery).
• Assign IoTConsensusV2 realtime replicateIndexForIoTV2 lazily at supply-time (and idempotently), with added unit tests.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
iotdb-core/datanode/src/test/java/org/apache/iotdb/db/pipe/source/dataregion/realtime/PipeRealtimeReplicateIndexAssignmentTest.java	Adds a unit test to validate lazy + idempotent replicate index assignment behavior.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/source/dataregion/realtime/assigner/PipeDataRegionAssigner.java	Removes eager replicate index assignment during event assignment.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/source/dataregion/realtime/PipeRealtimeDataRegionTsFileSource.java	Assigns replicate index (if needed) at supply() time.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/source/dataregion/realtime/PipeRealtimeDataRegionSource.java	Introduces shared lazy/idempotent replicate index assignment helpers.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/source/dataregion/realtime/PipeRealtimeDataRegionLogSource.java	Assigns replicate index (if needed) at supply() time.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/source/dataregion/realtime/PipeRealtimeDataRegionHybridSource.java	Assigns replicate index (if needed) at supply() time to avoid holes.
iotdb-core/consensus/src/test/java/org/apache/iotdb/consensus/iot/StabilityTest.java	Adds a test to ensure createLocalPeer tolerates an existing consensus directory.
iotdb-core/consensus/src/main/java/org/apache/iotdb/consensus/iot/IoTConsensus.java	Allows reuse of an existing consensus peer directory in createLocalPeer.
iotdb-core/confignode/src/test/java/org/apache/iotdb/confignode/procedure/env/RegionMaintainHandlerConsensusPipeTest.java	Adds tests verifying retry behavior changes based on DataNode status.
iotdb-core/confignode/src/main/java/org/apache/iotdb/confignode/procedure/env/RegionMaintainHandler.java	Uses node status to decide between full retry vs single-attempt RPC for deleting old peers.

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