In response to an ongoing BuildJet outage, consider migrating CI to
GitHub hosted runners.

Also includes revert of (causing flaky tests):
- https://github.com/zed-industries/zed/pull/35741

Downsides:
- Cost (2x)
- Force migration to Ubuntu 22.04 from 20.04 will bump our glibc minimum
from 2.31 to 2.35. Which would break RHEL 9.x (glibc 2.34), Ubuntu 20.04
(EOL) and derivatives.

Release Notes:

- N/A