Cargo: Handle errors properly in cargo-marker

[xFrednet]

cargo-marker interacts a lot with other programs or the file system. Therefore, it has to handle numerous Result<X, Y> types. Currently, every error is just mapped to a single ExitStatus enum, that provides very little information. This is not ideal...

• It might be good to use an existing library for error handling.
• Errors should provide as much information as possible.
• Only the CLI part of cargo_marker should "know" what an exit status is.

[xFrednet]

This issue should be a good first issue for everyone, that has a bit of experience with proper error handling in Rust. :)

[Veetaha]

I'd like to take this issue

[xFrednet]

You're very welcome to, feel free to add the dependencies you already mentioned previously :)