[Github] Add ability to filter jobs in job counting script

[boomanaiden154]

This patch adds a new flag pair, --filter-gha-runners, and --no-filter-gha-runners, that filters out all non-Github hosted runners so that we can actual counts of the Github runners, where we are actually limited.

[boomanaiden154]

This also depends on PyGithub/PyGithub#2902 (and probably them tagging a new release as well). Not sure exactly when that will happen.

[tstellar]

This also depends on PyGithub/PyGithub#2902 (and probably them tagging a new release as well). Not sure exactly when that will happen.

Will the script still work with older versions of pygithub if you don't use this new option?

[boomanaiden154]

Will the script still work with older versions of pygithub if you don't use this new option?

Good point. I was originally planning on just landing this after the version gets released, but just making sure that it works with the flag disabled (and making that the default) and landing it now probably makes a lot more sense. I've updated the patch to not enable the new flag by default, and add error handling for old versions indicating what the issue is on top of adding a TODO to remove the error handling once we're able to migrate to a PyGithub version with the patches that we need.