Fix pipe drop event discard with restart-aware committer keys

[Caideyipi]

Description

This PR fixes pipe event discard logic when dropping a pipe task by using CommitterKey instead of only (pipeName, creationTime, regionId).

Previously, queued/retry/batched events were matched only by pipe name, creation time, and region id, which could incorrectly
discard events from a restarted pipe task. This change propagates the full committer key through pending queues, sink
subtasks, batch builders, and sink implementations so discard checks can distinguish task restart generations.

Changes

• Use CommitterKey for dropped pipe task tracking and event matching.
• Propagate restart-aware discard APIs across pipe sink subtasks and connectors.
• Update async, sync, airgap, and websocket sinks to discard only matching pipe task events.
• Keep backward-compatible discard methods with wildcard restart time.

---

This PR has:

• been self-reviewed.
  • concurrent read
  • concurrent write
  • concurrent read and write
• added documentation for new or modified features or behaviors.
• added Javadocs for most classes and all non-trivial methods.
• added or updated version, license, or notice information
• added comments explaining the "why" and the intent of the code wherever would not be obvious
  for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold
  for code coverage.
• added integration tests.
• been tested in a test IoTDB cluster.

---

Key changed/added classes (or packages if there are too many classes) in this PR

[sonarqubecloud]

Quality Gate failed

Failed conditions
7.3% Duplication on New Code (required ≤ 5%)

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 56.32184% with 38 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.57%. Comparing base (0d1b838) to head (a20c1d3).
⚠️ Report is 13 commits behind head on master.

Files with missing lines	Patch %	Lines
.../payload/evolvable/batch/PipeTabletEventBatch.java	0.00%	7 Missing ⚠️
.../pipe/agent/task/subtask/sink/PipeSinkSubtask.java	25.00%	6 Missing ⚠️
...ink/protocol/airgap/IoTDBDataRegionAirGapSink.java	0.00%	3 Missing ⚠️
.../protocol/thrift/sync/IoTDBDataRegionSyncSink.java	0.00%	3 Missing ⚠️
...db/pipe/sink/protocol/websocket/WebSocketSink.java	0.00%	3 Missing ⚠️
...e/sink/protocol/PipeConnectorWithEventDiscard.java	0.00%	3 Missing ⚠️
...gent/task/subtask/sink/PipeSinkSubtaskManager.java	0.00%	2 Missing ⚠️
...d/evolvable/batch/PipeTransferBatchReqBuilder.java	50.00%	2 Missing ⚠️
...rotocol/thrift/async/IoTDBDataRegionAsyncSink.java	83.33%	2 Missing ⚠️
...n/task/subtask/SubscriptionSinkSubtaskManager.java	0.00%	2 Missing ⚠️
... and 4 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #17748      +/-   ##
============================================
- Coverage     40.59%   40.57%   -0.03%     
  Complexity     2574     2574              
============================================
  Files          5179     5180       +1     
  Lines        349979   350366     +387     
  Branches      44749    44803      +54     
============================================
+ Hits         142082   142153      +71     
- Misses       207897   208213     +316     

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