Use Cargo.toml instead of rust-project.json #1935
Description
We can generate a Cargo.toml file containing a [[bin]] entry for every exercise.
This should make things much smoother and less hacky, especially because we have many issues related to the language server.
This should also enable us to use Cargo instead of rustc to run the exercises. That would especially make Clippy exercises less of a trouble. This approach also allows us to easily add dependencies to the exercises in case we want to do so in the future.