[CRZbulabula]

Problem

RemoveDataNodesProcedure reported rollback as unsupported for every state. After commit-point rollback gating was introduced, a child migration failure at STOP_DATA_NODE skipped the parent cleanup, leaving failed DataNodes in Removing and failing the ConfigNode unit test on Linux and Windows.

Solution

• Allow rollback only at STOP_DATA_NODE, where the existing rollback hook restores failed node statuses and stops fully migrated nodes.
• Keep earlier states non-rollbackable so their existing retry and commit-point behavior is preserved.

Validation

• mvn -pl iotdb-core/confignode -am -Dtest=RemoveDataNodesProcedureTest#metadataRetryExhaustionRetriesFailedNodeStatusCleanup -DfailIfNoTests=false -Dsurefire.failIfNoSpecifiedTests=false test
• mvn spotless:apply -pl iotdb-core/confignode