Style for long type paths

Referred from https://github.com/rust-lang/rustfmt/pull/6494

A long type path could look like `long_type_path::long_type_path::long_type_path::long_type_path::long_type_path::long_type_path::long_type_path::long_type_path::long_type_path::long_type_path::Long` which currently would not get formatted, but this could exceed rustfmt's `max_width` setting.

How could this be handled?