ci: mv cirrus.yml to github yaml

[maflcko]

Seems odd to have two different yamls/providers. So just use a single one.

While moving, this:

• drops the caching, because cloning the repo takes longer than installing cargo.
• drops the skip on pull requests, because it seems nice to have the latest lint output on the master branch as well.

[polespinasa]

githum → github in pr title and commit title

[maflcko]

Thx, fixed

[maflcko]

MBR