Enable trimmed paths

[camsteffen]

Blocked on #7797.

This was initially attempted in #7668.

We probably should write an internal lint to detect trimmed path invocations that would ICE if a lint is not emitted (e.g. it is allowed). This would work by finding Ty as Display usages like type.to_string() or tcx.def_path_str calls that occur outside of span_clippy_lint.