Fix concurrent subscription consumer handshakes

[Caideyipi]

What is changed

• Serialize handshakes for the same subscription consumer identity and atomically transfer ownership to one connection.
• Give each consumer instance a transient, ordered consumer-instance-id shared by all of its DataNode handshakes, so every DataNode chooses the same winner even when requests arrive in different orders. Legacy clients retain arrival-order behavior, and the transient ID is removed before consumer attributes are persisted to ConfigNode.
• Fence the losing receiver with status 1919 so stale heartbeats, subscriptions, polls, commits, closes, and handshakes cannot affect the active consumer.
• Treat consumer fencing as a terminal client state: stop background workers and reconnect attempts, close only transport sessions, discard sibling parallel-poll results, and fail async commits with the original fencing exception without consuming their message iterable.
• Add English/Chinese messages and regression tests for concurrent and cross-DataNode handshake ordering, late handshakes/exits, client lifecycle, poll handling, and async commit handling.

Verification

• mvn spotless:apply (passed)
• git diff --check (passed)
• mvn -nsu test -pl iotdb-client/subscription '-Dtest=SubscriptionConsumerLifecycleTest,SubscriptionProviderStatusTest,SubscriptionConsumerConnectionFailureTest' '-DforkCount=0' (13 passed after rebasing onto current master)
• mvn -nsu test -pl iotdb-core/datanode '-Dtest=SubscriptionReceiverAgentTest,SubscriptionReceiverV1Test' '-DforkCount=0' (25 passed before the latest rebase; git range-diff confirms the server-side patch is unchanged)
• Full English and Chinese reactor compilation: pending the current PR CI run