Support #[coverage(off)] to exclude results

[zecakeh]

The coverage_attribute feature has switched from no_coverage to coverage(off) in rust-lang/rust#114656.

This adds support for the new format.

I wasn't sure if the old format should be removed right away. It might need a deprecation first.

Closes #1591.

[xd009642]

I try to go rather conservative on deprecations, so if the compiler still supports #[no_coverage] then we'll keep it in. If it doesn't keep it in if it's low effort otherwise assess and decide

[zecakeh]

no_coverage is not supported anymore by the compiler.

[xd009642]

Cool we'll keep it in for now I'll just add a note about it after merge thanks for this looks good to me 👍