feature: allow providing runner registration token and disabling querying the API

[agaffney]

Summary

This will allow someone to add a new runner via the Github UI to get the registration token, and then avoid needing to provide a PAT for their own Github account or have the role make any calls the Github API

Issue Type

Feature Idea

[mackenzie-remote]

I can confirm that I was able to successfully register a repository runner using this role by going to settings on my repo, /settings/actions/runners -> hitting "New self-hosted runner" and using the token in the configure step with the env variable PERSONAL_ACCESS_TOKEN.

I did this by commenting out:
Get registration token (RUN ONCE) -> (got a 401 Bad Credentials).
Check currently registered runners for repo (RUN ONCE)

and any steps that referenced the now null registered_runners and registration variables.