[pkg/stanza]: allow max_batch_size to be 0 for unlimited batching in recombine

[MoosaTae]

Description

Allow setting max_batch_size: 0 in the recombine operator to disable the batch size limit, enabling unlimited batching.

• Modified condition in transformer.go to check maxBatchSize > 0 before applying the limit
• Added test case TestMaxBatchSizeUnlimited to verify the new behavior

Link to tracking issue

Fixes #43982 (partial - enables the feature)

Testing

• Added TestMaxBatchSizeUnlimited test

Documentation

Configuration Example

receivers:
  filelog:
    operators:
      - type: container

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The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: MoosaTae / name: Sadit Wongprayon (e337fe11101678ce636975427b63c45c2f07b9b0)

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