Enforce reviewer comments for file groups containing files with changes requested

[LFISHER7]

You don't currently have to write a reviewer comment for a file group that contains a file you have requested changes for. This means a request can be returned with changes required, but no detail on what changes.

Reviewers should each have to write a comment before they submit their request in these cases. There should also be a public comment before the request is returned.

See this Slack thread for more detail.

[LFISHER7]

Similarly, it looks like the requester is not required to add a new comment describing changes they make following a file being marked as requiring changes. The requester should have to write a comment before they can resubmit a file group containing such a file

[LFISHER7]

I think they can however, update the context and controls. When they do this, it's not obvious that's what they've done and what the changes are. I think the context/controls should remain fixed across review rounds, and ask for any changes to context/controls to be indicated as comments