Add a token to avoid rate limits on tests

[choldgraf]

This cleans up some of our token reading code and un-breaks tests in the process. Here's what this does:

• Adds a TOKEN_READONLY so that we don't hit rate limits as quickly.
• This adds the constraint that this token will only be used on a PR from a non-fork, so it's only a short-term fix. But it confirms that our test suite now passes.

[bsipocz]

This is not great then, IMO fork based workflow should be encouraged for everyone in general so to remove the "us and them" distinctions between contributors and the core team.

[bsipocz]

(I don't necessarily say that for this repo as it should be a low traffic utility; but in general for JB)

[choldgraf]

I agree, I am just trying to get this un-stuck here! The other option would be to re-configure out test suite so that it doesn't hit API rate limits as quickly but that feels like something I don't have the bandwidth to fix right now

[choldgraf]

I've updated this PR so that it will revert to the old behavior if the PR is from a forked repository, that way we'll use the PAT's rate limit for non-forked calls (like releases etc) and we'll use the default github limit for all others.

[choldgraf]

superceded by #134