This is a aspect of Rust that frequently trips up people who are not
aware of it yet. This diagnostic attempts to explain what's happening
and why the lifetime constraint, that was never mentioned in the source,
arose.
Tweak spans for self arg, fix borrow suggestion for signature mismatch
1. Adjust a suggestion message that was annoying me
2. Fix#112503 by recording the right spans for the `self` part of the `&self` 0th argument
3. Remove the suggestion for adjusting a trait signature on type mismatch, bc that's gonna probably break all the other impls of the trait even if it fixes its one usage 😅
