HBASE-30389 Fix regionLocation inconsistency when switching master

[Huginn-kio]

HBASE-30389

Summary

Normalize stale region locations while the active master rebuilds assignment state from
hbase:meta after failover.

Root cause

AssignmentManager.RegionMetaLoadingVisitor.visitRegionState copies the region server location
from hbase:meta into RegionStateNode, while only states with current-host semantics are added to
the per-server assignment state. A stale location can therefore remain visible for CLOSED or
other non-online regions.

Fix

• Normalize the loaded location to null for states without current-host semantics.
• Preserve lastHost for locality and recovery decisions.
• Add regression coverage for CLOSED, OPEN, and implicit OFFLINE states across master failover,
  plus a split recovery case.

Testing

• mvn --batch-mode -Dtest=TestAssignmentManagerLoadMetaRegionState,TestMasterAbortWhileSplittingRegion -Dsurefire.rerunFailingTestsCount=0 -Dsurefire.parallel.forcedTimeout=900 -Dsurefire.shutdown=kill -DtrimStackTrace=false -DforkCount=0.5C -am -pl ./hbase-server test
  • 5 tests run, 0 failures, 0 errors.
• mvn --batch-mode -pl hbase-server -DskipTests apache-rat:check
  • Passed.

Compatibility

• No public API changes.
• No configuration, persisted-format, or wire-format changes.