[SPARK-50967][SS] Add option to skip emitting initial state keys within the FMGWS operator

[anishshri-db]

What changes were proposed in this pull request?

Add option to skip emitting initial state keys within the FMGWS operator

Why are the changes needed?

Without this change, user does not have an easy way of filtering initial state rows emitted as part of the first batch.

Does this PR introduce any user-facing change?

No

How was this patch tested?

Added unit tests

[info] Run completed in 15 seconds, 349 milliseconds.
[info] Total number of tests run: 4
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 4, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 51 s, completed Jan 23, 2025, 4:26:03 PM

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

No

[anishshri-db]

cc - @HeartSaVioR - PTAL, thx !