Pull GitHub comments from our own API

[benjaminleonard]

Through CIO, or it's own runner, we should mirror the comments from the GitHub API perhaps also moving the logic that rearranges them into threads there too.

Currently RFD 4 (with 248 comments) can take 15s+ to retrieve. Response times increase based on the number of comments, but we can't just get the first page. We want all of the inline comments visible, but currently we have to request them all, outdated or not.

Simply moving this to it's own API would speed this up massively, but we can likely optimise it further with a paginated API for the full list of comments, and only returning the count and inline comments on page load.