[FLINK-32695] Moved TestSource in TypeFillTest to SourceV2

[Poorvankbhatia]

What is the purpose of the change

This pull request migrates TypeFillTest from the deprecated SourceFunction API to the new Source V2 API

Brief change log

• TypeFillTest.java: Replaced TestSource extends SourceFunction with NoopSource implements Source<T, SourceSplit, Void> for type inference testing

Verifying this change

This change is already covered by existing tests:

TypeFillTest.java:

• All type inference validation tests continue to pass, verifying InvalidTypesException is thrown for sources without explicit type information
• Tests confirm .returns() method properly resolves type information for generic sources

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:

• 6ab4030 Azure: FAILURE

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