Rollup of 6 pull requests

[emilyalbini]

Successful merges:

• Add unix::process::CommandExt::arg0 #66512 (Add unix::process::CommandExt::arg0)
• GitHub Actions: preparations, part 1 #66569 (GitHub Actions: preparations, part 1)
• Drive-by cleanup in region naming #66684 (Drive-by cleanup in region naming)
• Add some comments to panic runtime #66694 (Add some comments to panic runtime)
• tidy: Remove unused import #66698 (tidy: Remove unused import)
• Move ErrorReported to rustc_errors #66720 (Move ErrorReported to rustc_errors)

Failed merges:

r? @ghost