Add --suites filter to generate_reference_results

[Geethapranay1]

Closes #711

Changes

1. tools/tests/generate_reference_results.py — added --suites argument (comma-separated, optional) to filter which test suites to generate reference results for. When not provided, all suites run (backward compatible).
2. generate_reference_results_workflow.yml — added optional suites input. When provided, passes --suites to the script and uses selective git add --update to only commit modified files. When empty, behavior is unchanged.
3. generate_reference_results_manual.yml — added suites input field for the manual trigger UI.

Testing

1. full docker test passed for --suites filter

only 3 elastic tube tests ran not all 10

2. error handling for invalid suite name

3. backward compatible default behavior (no --suites)

4. --help shows a new argument

Checklist:

• I added a summary of any user-facing changes (compared to the last release) in the changelog-entries/<711>.md.
• I will remember to squash-and-merge, providing a useful summary of the changes of this PR.

[Geethapranay1]

hi @MakisH
this pr solves the #711 issue.
check once and let me know if any further requirements needed in the pr.