[To dev/1.3] [Pipe] Restore sink progress under memory pressure (#18640)

[Caideyipi]

Description

Backport #18640 to dev/1.3 by cherry-picking e2ac222.

Restore sink-batch forward progress

#18582 changed the memory reservation owned by PipeTabletEventBatch from a normal PipeMemoryBlock to a PipeTabletMemoryBlock. This made sink-batch growth subject to the tablet data-structure admission thresholds. Once retained tablet memory crossed that sub-quota, a sink batch could no longer grow enough to transfer and acknowledge events, so the retained/floating memory could not be released either.

This change restores the batch reservation to a normal pipe memory block. Tablet and TsFile allocations remain bounded by their data-structure thresholds, while sink batches can use the remaining non-floating memory to make downstream progress and release retained events.

Back off memory-timeout retries

PipeAbstractSinkSubtask previously retried MEMORY_TIMEOUT failures immediately while applying backoff to the other transient resource failures. Memory timeouts now use the existing non-report exception backoff after logging the transient condition.

The cherry-pick had one conflict in PipeAbstractSinkSubtask; the resolution preserves the dev/1.3 logging code and applies the upstream backoff behavior.

Regression coverage

• mvn spotless:apply -pl iotdb-core/node-commons,iotdb-core/datanode: passed.
• mvn test -pl iotdb-core/node-commons -Dtest=PipeSleepIntervalTest: passed (4 tests).
• git diff origin/dev/1.3..HEAD --check: passed.
• PipeTransferBatchReqBuilderTest was attempted, but the standalone DataNode build stopped before tests because the local 1.3.7-SNAPSHOT dependency artifacts are older than the current dev/1.3 sources (missing unrelated generated Thrift and cross-module APIs). The changed DataNode source itself produced no compiler error; CI will build it with reactor-consistent dependencies.

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This PR has:

• been self-reviewed.
• added unit tests for the changed code paths.

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Key changed/added classes

• PipeTabletEventBatch
• PipeAbstractSinkSubtask
• PipeTransferBatchReqBuilderTest
• PipeSleepIntervalTest