[SPARK-55402][SS] Move streamingSourceIdentifyingName from CatalogTable to DataSource

[ericm-db]

What changes were proposed in this pull request?

This PR refactors the streamingSourceIdentifyingName field to move it from CatalogTable into DataSource as a constructor parameter. The changes include:

1. DataSource.scala: Added streamingSourceIdentifyingName as an optional constructor parameter
2. StreamingRelation.scala: Updated StreamingRelation.apply() to read the name from DataSource instead of CatalogTable
3. DataSourceStrategy.scala: Modified FindDataSourceTable.getStreamingRelation() to pass the name directly to DataSource constructor instead of copying it onto CatalogTable
4. CatalogTable (interface.scala): Removed the streamingSourceIdentifyingName field entirely
5. Test updates: Updated test files to reflect the new architecture

Why are the changes needed?

streamingSourceIdentifyingName represents query-specific metadata (which source name was assigned in a particular streaming query plan), not an intrinsic property of the table itself. Storing it in CatalogTable breaks table equality semantics:

• Two references to the same table in a single query can have different streamingSourceIdentifyingName values
• This causes them to compare as unequal via CatalogTable.equals()
• This can impact multi-statement transactions and any caching/deduplication logic that relies on CatalogTable equality
  By moving this field to DataSource (which is already query-specific), we restore proper catalog table equality while maintaining the ability to track streaming source identifying names for stable checkpoints.

Does this PR introduce any user-facing change?

No

How was this patch tested?

Unit tests

Was this patch authored or co-authored using generative AI tooling?

Generated-by: Claude Opus 4.6

[github-actions]

JIRA Issue Information

=== Task SPARK-55402 ===
Summary: Move streamingSourceIdentifyingName from CatalogTable to DataSource
Assignee: None
Status: Open
Affected: ["4.2.0"]

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[brkyvz]

LGTM minus one comment