* rust-analyzer in non-cargo projects
rust-analyzer can also be used in non-cargo projects. This requires a
rust-project.json file in the project root [1].
Make the rust-analyzer linter search for a rust-project.json file if no
Cargo.toml file could be found.
[1]: https://rust-analyzer.github.io/manual.html#non-cargo-based-projects
* Document rust-analyzer without cargo
* Test rust-analyzer with non-cargo projects
Change the other rust tests to match the new directory structure of the
test files.
