[Kafka] Clean up code in the `flink-cdc-pipeline-connector-kafka` mod… #2325

Job	Run time
License Check	4m 41s
Pipeline Connectors Unit Tests 2.x / test (11, 2.2.0, doris, elasticsearch, fluss, iceberg, kafka, maxcompute, mysql-pipeline, oceanba...	1h 2m 45s
Source Unit Tests / test (11, generic, db2, mongodb)	43m 5s
Pipeline Unit Tests / test (11, generic, doris, elasticsearch, fluss, hudi, iceberg, kafka, maxcompute, mysql-pipeline,...	1h 2m 46s
Source Unit Tests / test (11, generic, mysql-source)	1h 31m 3s
Common Unit Tests 2.x / test (11, 2.2.0, core)	13m 43s
Source Unit Tests / test (11, generic, postgres-source, oceanbase-source, tidb, vitess)	37m 7s
Source Unit Tests / test (11, generic, oracle, sqlserver)	31m 29s
Common Unit Tests / test (11, generic, core)	13m 17s
Source Unit Tests 2.x / test (11, 2.2.0, mysql-source)	42m 24s
Source Unit Tests 2.x / test (11, 2.2.0, postgres-source, oceanbase-source, tidb, vitess)	23m 40s
Source Unit Tests 2.x / test (11, 2.2.0, db2, mongodb)	34m 23s
Source Unit Tests 2.x / test (11, 2.2.0, oracle, sqlserver)	39m 23s
Source E2E Tests / test (11, 1.20.3, source_e2e)	21m 15s
Pipeline E2E Tests 2.x (1-Parallelism) / test (11, 2.2.0, pipeline_e2e)	1h 2m 53s
Pipeline E2E Tests 2.x (4-Parallelism) / test (11, 2.2.0, pipeline_e2e)	59m 19s
Pipeline E2E Tests (4-Parallelism) / test (11, 1.20.3, pipeline_e2e)	1h 18m 49s
Pipeline E2E Tests (1-Parallelism) / test (11, 1.20.3, pipeline_e2e)	1h 19m 43s
	13h 21m 45s

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