[FLINK-32695] [Tests] Migrated TableFactoryHarness.ScanSourceBase to Source V2

[Poorvankbhatia]

What is the purpose of the change

This PR migrates legacy SourceFunction and SinkFunction implementations in table planner tests from the deprecated legacy APIs to the modern FLIP-27 Source API

Brief change log

• Migrated TableFactoryHarness.ScanSourceBase from SourceFunctionProvider to SourceProvider with DataGeneratorSource
• Migrated TableFactoryHarness.SinkBase from SinkFunctionProvider to SinkV2Provider with TestSinkV2
• Implemented custom Source V2 in CommonExecSinkITCase.TestSource to preserve timestamp ordering
• Updated BuiltInAggregateFunctionTestBase to use DataGeneratorSource instead of legacy SourceFunction

Verifying this change

Existing tests already cover these changes:

• BuiltInAggregateFunctionTestBase: ModuleITCase, HashcodeITCase, MiscAggFunctionITCase, ArrayAggFunctionITCase, JsonAggregationFunctionsITCase, PercentileAggFunctionITCase
• CommonExecSinkITCase: testStreamRecordTimestampInserterSinkRuntimeProvider and other timestamp-related tests
• TableFactoryHarness: All dependent test cases using the harness framework

All tests pass.

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

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• 2bac5e3 Azure: SUCCESS

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