[Fix] Keep heartbeat alive when metadata lease is fenced

[Caideyipi]

Description

• build schema quota count maps on snapshots and publish them to the heartbeat response only after both device and series counts succeed
• catch MetadataLeaseFencedException while collecting schema counts so the DataNode heartbeat can still complete
• omit both region device and series usage maps after this failure, preventing ConfigNode from applying partial schema count updates
• emit a localized warning and add regression coverage for both method-level atomicity and the fenced-heartbeat path

Tests

• mvn -nsu test -pl iotdb-core/datanode -Dtest=DataNodeInternalRPCServiceImplTest#testHeartbeatSkipsSchemaUsageWhenMetadataLeaseIsFenced
• mvn -o -nsu test-compile -pl iotdb-core/datanode -P with-zh-locale -DskipTests

[sonarqubecloud]

Quality Gate failed

Failed conditions
C Reliability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

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