Janis/inline comments/feature flag

What does this MR do and why?

Introduce a feature flag for a feature that will enable inline comments in work items. This MR does not introduce any feature itself, just the flag.

References

Issue: #632839

Feature Flag Rollout Issue: #632840

Screenshots or screen recordings

No UI Changes

How to set up and validate locally

1. Open any work item, verify it works as it did previously.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.