chore: Split sec_mark_dropped_findings_as_resolved FF

What does this MR do and why?

FF rollout issue [Feature flag] Enable sec_mark_dropped_findings... (#387577 - closed)

Split [Feature flag] Enable sec_mark_dropped_findings... (#375128 - closed) into separate feature flag for job scheduler and worker to better assess performance

Previously the scheduler of the worker jobs was behind the same flag as the worker jobs themselves but we want to control these independently so we can assess the performance of the scheduler prior to enabling the feature itself.

MR acceptance checklist

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