Add ops feature flag to toggle search curation dry_run parameter

What does this MR do and why?

Adds the feature flag search_curation_dry_run to toggle search curation dry_run parameter.

These are related MRs to this process:

• Add dry run capability: !103959 (merged)
• Add inclusion parameter to support excluding everything besides specified indices: !103951 (merged)
• Add feature flags to toggle which indices should be added to inclusion parameter: !104423 (merged)
• Add an ops feature flag that toggles dry_runparameter in Search::IndexCurationWorker: !104321 (merged) 👈

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.