Improving GitHub API usage in CI

[mahmoud]

As a followup to #227, it looks like the awesome new CI setup has one weak point: merging multiple PRs at once exhausts the request limit and all parallel actions fail.

A few fixes come to mind:

1. Freeze in the emeritus status projects (write a command to do this), so that if a project is emeritus and has all the necessary keys, we don't fetch any of it from github anymore, even if the gh_url is there.
   • This probably cuts requests in half.
2. Add a flag to only fetch/add projects in the YAML that aren't in the JSON.
   • If this commits back, it's going to conflict, so probably don't commit. Let the nightly job pick it up.
3. Solution 2 + switch to a directory-based approach so every project gets its own little JSON file.
   • I was thinking a directory could work well for avoiding conflicts in the source yaml, too.

Each of these could be its own PR, so choose your own adventure.

[MattTheCuber]

What are your thoughts on me doing this in #237? Would it be better to do this in a separate PR after #237?

[mahmoud]

@MattTheCuber if it's easier to fold it in to the existing PR, go for it! Which approaches were you thinking? I think number 3 might be a bit ambitious for #237.

[MattTheCuber]

Yeah, I'm thinking all 3 approaches would be optimal. I'll probably save for after #237