Allow configuring "Enable Comments on Suspect Pull Requests" on a per-repo basis

### Problem Statement

This is regarding the Github integration in Sentry. It is currently only possible to enable this toggle for the entire integration (e.g. all repositories connected) in the "features" tab. We have an organization with a lot of repos, and some can't or do not want this feature enabled which events it from being enabled in others.

### Solution Brainstorm

It would be great to have a toggle per-repo or an opt-in/opt-out list to select which repos to comment on suspect commit PRs.

### Product Area

Unknown

Start by tracing the GitHub integration's organization-wide "Enable Comments on Suspect Pull Requests" toggle in the features tab and the repository configuration entry points. Done means the setting can be selected per repository or through an explicit opt-in/opt-out list, while existing repositories retain expected behavior.

Written by the indexing model from the issue text.