Remove feature flags to related to hackathon rules

[mesembria]

Worked required to release several of the rules from the rule hackathon back in Dec.

• Remove feature flag and document PR comment alert
• Remove feature flag and document git PR diff ingester
• Remove feature flag and document rego tar.gz functions

And anything else minor that needs to be done to make these usable to users outside of Stacklok. Any work around healthcheck bundle is excluded from this story.