feat(java): add batch consume support for PushConsumer

[qianye1001]

Which Issue(s) This PR Fixes

Fixes #1225

Brief Description

This PR adds first-class batch consumption support for PushConsumer in the Java client, controlled by a BatchPolicy.

PushConsumer — Batch Consume Service

• BatchConsumeService: accumulates messages from all ProcessQueues into a single BatchBuffer, flushing to BatchMessageListener when any threshold is met (count, bytes, or timeout).
• BatchBuffer: encapsulated accumulation buffer with lock-based concurrency, scheduled timeout flush, forward-progress guarantee (single oversized message is still flushed).
• BatchConsumeTask: Callable that invokes BatchMessageListener with interceptor hooks.
• New BatchMessageListener interface and PushConsumerBuilder.setBatchMessageListener().
• FIFO mode support: in FIFO mode, only one batch is in-flight at a time, preserving strict ordering.
• Graceful shutdown: close() flushes all remaining buffered messages before the consumer shuts down.

BatchPolicy

Policy with maxBatchCount, maxBatchBytes, maxWaitTime. Builder pattern with sensible defaults.

A batch is flushed when any condition is met:

1. Message count reaches maxBatchCount.
2. Total body bytes reach maxBatchBytes.
3. Time since first buffered message reaches maxWaitTime.

How Did You Test This Change?

• BatchConsumeServiceTest: 14 unit tests covering count/bytes/timeout triggers, corrupted message discard, multiple batches from single consume, single oversized message flush, batch failure, close flush, multiple ProcessQueues, FIFO ordering, FIFO close, FIFO timeout-respects-inflight.
• BatchConsumeTaskTest: 5 unit tests covering success/failure/exception/null-return scenarios with interceptor hooks, and batch size passthrough.
• BatchPolicyTest: 11 unit tests covering constructors, builder, validation, toString.
• PushConsumerBuilderImplTest: added 4 tests for batch builder validation (no listener, both listeners, null listener, null policy).
• All tests pass: mvn clean test -pl client-apis,client — 307 tests, 0 failures, 0 checkstyle violations.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.69528% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.36%. Comparing base (4076e2b) to head (83f867c).
⚠️ Report is 117 commits behind head on master.

Files with missing lines	Patch %	Lines
...mq/client/java/impl/consumer/PushConsumerImpl.java	20.00%	12 Missing ⚠️
...nt/java/impl/consumer/PushConsumerBuilderImpl.java	43.75%	7 Missing and 2 partials ⚠️
...ocketmq/client/java/impl/consumer/BatchBuffer.java	93.87%	1 Missing and 5 partials ⚠️
...client/java/impl/consumer/BatchConsumeService.java	95.65%	3 Missing ⚠️
...etmq/client/java/impl/consumer/ConsumeService.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1226      +/-   ##
============================================
+ Coverage     53.26%   54.36%   +1.09%     
- Complexity      651      854     +203     
============================================
  Files           208      223      +15     
  Lines         14303    14669     +366     
  Branches       5845     5617     -228     
============================================
+ Hits           7619     7975     +356     
+ Misses         6308     6286      -22     
- Partials        376      408      +32     

Flag	Coverage Δ
java	63.79% <86.69%> (+2.10%)	⬆️

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[qianye1001]

Closing in favor of a new PR with improved implementation: cleaner class hierarchy (BatchConsumeService + FifoBatchConsumeService via inheritance), precise batch splitting with forward-progress guarantee, Builder pattern for BatchPolicy, and whole-batch FIFO retry semantics.