[fix][fn] Fix the --batch-builder not working error for functions

[jiangpengcheng]

Fixes #21022

Main Issue: #xyz

PIP: #xyz

Motivation

the --batch-builder argument not working for functions, the reason is that it just save it to the FunctionConfig, and the backend doesn't use the FunctionConfig.batchBuilder.

Modifications

check the FunctionConfig.batchBuilder in FunctionConfigUtils#convert method to set batch builder for the producer spec

Verifying this change

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This change is a trivial rework / code cleanup without any test coverage.

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This change is already covered by existing tests, such as (please describe tests).

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This change added tests and can be verified as follows:

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• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

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• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
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• Anything that affects deployment

Documentation

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Matching PR in forked repository

PR in forked repository: jiangpengcheng#14