Rollup merge of #140370 - WaffleLapkin:unqualified, r=jdonszelmann

Improve diagnostics for usage of qualified paths within tuple struct exprs/pats

For patterns the old diagnostic was just incorrect, but I also added machine applicable suggestions.

For context, this special cases errors for `<T as Trait>::Assoc(..)` patterns and expressions (latter is just a call). Tuple struct patterns and expressions both live in the value namespace, so they are not forwarded through associated *types*.

r? ``@jdonszelmann``

cc ``@petrochenkov`` in rust-lang/rust#80080 (comment) you were wondering why it doesn't work for types, that's why — tuple patterns are resolved in the value namespace.

Author: GuillaumeGomez