Use new nf-test features

[edmundmiller]

• ci: Attempt to split everything out
• ci: Add changed since, sharding, and ci
• ci: Add filter to try to get jobs split up
• ci: Switch to only-changed
• ci: See if follow-dependencies works without "related-tests"

[edmundmiller]

We do have adamrtalbot/detect-nf-test-changes as a fallback option?

That's what we're currently using, so I don't really see it as a fallback 😆 It works fine, I think the sharding can work better and waste less resources spinning up a runner for each test instead of spinning up a consistent amount per PR.

That would close #391 as well, and might encourage people to make smaller PRs if we're only giving them 9 CI runners per PR anyway.

[edmundmiller]

Current things blocking this is nf-core/tools#3140 or we can give up and keep the paths-filter step for that

[edmundmiller]

Removed the need to use nf-core lint with pre-commit, as that wasn't truely blocking this from getting merged.

We can make a follow up issue to run every linting step through pre-commit.

[maxulysse]

Looking good, there's still some leftover comments in the nf-test yml, but I like it