Fix Node.js' code coverage/code coverage job #35646

• Version: 15.x.x
• Platform: All
• Subsystem: test

The problem(s)

1. new file paths are breaking the coverage reporting

File paths for Node.js' own files now have this form node:/internal/cluster/shared_handle:

• there's now anode: prefix.
• there's no longer a .js prefix.

I will happily fix this problem in the test reporter, but could someone point me towards where these changes were made (@watilde, @guybedford?) -- I want to make sure I link to the change in the reporter codebase.

2. nightly coverage is broken again

Coverage has been broken for several nights in a row. I believe this is due to an unrelated CI/CD upgrade?

Suggested fix

1. let's update c8 to support the new path format (I've tested that this fix is pretty trivial).
2. let's move code coverage to GitHub Actions (It seems like we need to fix Jenkins once every few months, and I can't see a reason why not to use actions).

CC: @nodejs/testing