Don't trim the crate name from the output

[jyn514]

Especially in workspaces, trimming the crate name is very confusing compared to the alternative. Without the crate name:

Found invalid urls in struct.FileError.html:
	Fragment #tymethod.deref at struct.FileError.html does not exist!
Found invalid urls in struct.CheckContext.html:
	Fragment #tymethod.init at struct.CheckContext.html does not exist!
Found invalid urls in struct.FileError.html:
	Fragment #tymethod.deref at struct.FileError.html does not exist!

With:

Found invalid urls in deadlinks/struct.MainArgs.html:
	Fragment #tymethod.deref at deadlinks/struct.MainArgs.html does not exist!
Found invalid urls in deadlinks/shared/struct.PicoError.html:
	Fragment #tymethod.deref_mut at deadlinks/shared/struct.PicoError.html does not exist!
Found invalid urls in cargo_deadlinks/struct.FileError.html:
	Fragment #tymethod.deref at cargo_deadlinks/struct.FileError.html does not exist!

The issue is that cargo-deadlinks is calling walk_dir on a single crate at a time (to avoid checking more crates than necessary, e.g. if you have a shared target dir):

cargo-deadlinks/src/bin/cargo-deadlinks.rs

Line 159 in 73de1df

if walk_dir(&dir, &ctx) {

which means that whole directory prefix is stripped:

cargo-deadlinks/src/lib.rs

Line 84 in 73de1df

err.shorten_all(dir_path);

Not sure what the correct fix is. Maybe the library can add yet another argument to prefix the shortened name with the crate name?