[APIView][Feature Request] Consolidate review comments and send one email notification

Currently, an email notification is sent for each comment on the APIView. It would be nice to provide an option to consolidate all comments into a single notification and then submit the review.

Start by tracing the APIView email-notification flow and how review comments are submitted. Determine where an option for consolidating comments belongs, then define the expected single-email behavior and verify that submitting the review still works correctly.

Written by the indexing model from the issue text.