feat: support Kafka protocol for functions #893

Job	Run time
integration (integration test, .ci/tests/integration/e2e.yaml)	14m 19s
integration (integration test with tls, .ci/tests/integration/e2e_with_tls.yaml)	14m 19s
integration (integration test with oauth2, .ci/tests/integration-oauth2/e2e.yaml)	14m 19s
integration (integration test with downloader, .ci/tests/integration-oauth2/e2e_with_downloader.y...	14m 19s
	57m 16s

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