[feature] Natively testrunner

[otavioschwanck]

a big part of a dev life is run tests. Would be awesome to have a vim-test like for helix natively.

[kirawi]

#2934 is related.

[matklad]

microsoft/language-server-protocol#944 is also related

[pascalkuthe]

I think any decent test runner would need an integrated terminal (#4649) to ensure the output is displayed correctly and updated continuously. Once thing that would be pretty nice to have in combination with this is for gf to respect line numbers (so you could jump right to the location of a backtrace like foo.rs:239 similar to what intellij allows)

Also somewhat related: #5063 as some LSP offer code lenses for running particular tests. But as @matklad mentioned there is no nice standardized solution we could merge into helix core.

[filipdutescu]

I think it would also be good to tie it in with DAP support. I find that more often than not when I run a test I'm doing it to debug some behaviour in a reproducible context, if that makes sense.