Describe the issue this Pull Request addresses

Closes #19401.

The Flink table-format and source-reader read paths lacked focused coverage for partition paths, CDC iteration, schema reconciliation, COW split planning, Lance reads, and source split-reader lifecycle behavior. The added CDC coverage also exposed two correctness gaps: an empty CDC file split could stop iteration before later changes, and truncated image bytes could cause an unbounded skip loop.

Summary and Changelog

• Add and extend focused tests for table-format and source-reader paths, including partition parsing and pruning, schema reconciliation, COW split planning, CDC image caching and iteration, source enumeration, expression conversion, split-reader lifecycle, projections, exception paths, and resource cleanup.
• Add TestHoodieRowDataLanceReader for metadata, row-key filtering, Arrow batch iteration, schema validation, and resource cleanup.
• Make CdcFileSplitsIterator advance through empty child iterators until it finds a row or exhausts all file splits.
• Make BytesArrayInputView throw EOFException when truncated input prevents a requested skip from making progress.

Targeted local JaCoCo line coverage:

The JaCoCo-enabled reactor run passed 212 tests with no failures, errors, or skips:

mvn -Punit-tests -Djacoco.skip=false \
  -pl hudi-flink-datasource/hudi-flink -am \
  -Dtest=TestFilePathUtils,TestCdcImageManager,TestCdcIterators,TestInternalSchemaManager,TestCopyOnWriteInputFormat,TestRecordIterators,TestHoodieSource,TestIncrementalInputSplits,TestExpressionEvaluators,TestHoodieSplitReaderFunction,TestHoodieCdcSplitReaderFunction,TestHoodieRowDataLanceReader,TestInputFormat \
  -Dsurefire.failIfNoSpecifiedTests=false \
  -DskipITs -DskipSparkTests -DskipScalaTests test

Impact

• Functional impact: CDC readers no longer stop at empty file splits, and truncated image input fails fast with EOFException instead of hanging.
• Maintainability: Focused tests document the supported table-format and source-reader branches and their resource ownership.
• Extensibility: The new Lance reader test fixture makes additional projections, filters, and metadata cases easier to add.

Risk Level

Low. The production changes are limited to CDC iterator boundary handling and an EOF guard. The affected classes and source-reader caller were covered by targeted tests, and the complete 212-test JaCoCo run passed.

Documentation Update

None.

Contributor's checklist

• Read through contributor's guide
• Enough context is provided in the sections above
• Adequate tests were added if applicable