Add CoPilot review processes

[slifty]

We may want this to cover (1) major change detection; (2) is documentation properly updated.

[slifty]

One detail that has come up for this is some confusion related to who exactly is able to trigger copilot reviews. If the individual dev needs it, we need to ensure our core team has that access.

In the long run it would be great to understand what the potential for open / self hosted models are for this type of behavior, but to be clear that isn't a blocker to short term progress.