[sn-platform][sn-platform-slim] Add if statement for customWorkerConfig

[jiangpengcheng]

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Motivation

PulsarBroker doesn't allow empty value for spec.config.function.customWorkerConfig, so only pass it when it's not empty

Modifications

Add if statement to the broker.functionmesh.customWorkerConfig

Verifying this change

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• Added integration tests for end-to-end deployment with large payloads (10MB)
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