i915g: Make it basically work again, add optional CI

With !10153 (merged) it would be nice if we had an i915 driver that distros could use without relying on the LTS repo, and with !8044 (merged) I would like to be sure that I'm not totally breaking this driver, so that led me to ebaying an old G33, setting it up as a shared runner, and putting together the CI expectations for it. In the process, I couldn't help but fix a few bugs.