unpaginate repos list for commit/diff search

Created by: camdencheek

This collects the list of repos for commit/diff search before executing the searches. This is necessary because we need to be able to error if the number of repos to be searched is above the limit. Currently, searches with too many repos will start searching, then time out, returning no error. This is causing a massive increase in load on gitserver with no way to identify which monitors are causing the issue.

This is a temporary measure, and will be reverted to the previous implementation once we identify the bad code monitors that should be disabled. This will add a bit of latency while it exists in this state.