Merge #126

126: cargo-marker: add git support r=xFrednet a=Niki4tap

Its been a while since I've worked on this, but I've finally took the time to finish it.

This PR adds git support to marker so this now works:
```toml
[workspace.metadata.marker.lints]
marker_lints = { git = "https://github.com/rust-marker/marker" }
```

It makes use of [`cargo_fetch`](https://github.com/Niki4tap/cargo_fetch) library which I made for this specific use-case, which is essentially just a thin wrapper around `cargo` library (so the builds are now way slower :p).

I'll try to maintain the library to my best capacity, and prioritize marker's goals whenever needed.

Addition of the library also technically allows for any kind of package to be downloaded, so this also *technically* supports registries, though this PR does not implement it, because this is blocked on marker APIs being released.

---

In total this checks out... *\*looks up the issue\**... one task from #81!
But also *technically* closes <!-- do not close this issue github please --> #87 whenever APIs are published.

review side note: most changes are from `Cargo.lock`

Co-authored-by: Niki4tap <[email protected]>

Author: bors[bot]