Convert custom ability feature flag actor to instance type

What does this MR do and why?

This converts the custom ability feature flag checks to an instance actor. Toggling feature flag status or rolling out incrementally can have odd side effects, so custom ability feature flags should only be used when the ability is a work in progress and enabled globally when the ability is ready.

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

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.

Related to #567852 (closed) #565702