Auto merge of #87244 - jackh726:issue-71883, r=estebank

Better diagnostics with mismatched types due to implicit static lifetime

Fixes #78113

I think this is my first diagnostics PR...definitely happy to hear thoughts on the direction/implementation here.

I was originally just trying to solve the error above, where the lifetime on a GAT was causing a cryptic "mismatched types" error. But as I was writing this, I realized that this (unintentionally) also applied to a different case: `wf-in-foreign-fn-decls-issue-80468.rs`. I'm not sure if this diagnostic should get a new error code, or even reuse an existing one. And, there might be some ways to make this even more generalized. Also, the error is a bit more lengthy and verbose than probably needed. So thoughts there are welcome too.

This PR essentially ended up adding a new nice region error pass that triggers if a type doesn't match the self type of an impl which is selected because of a predicate because of an implicit static bound on that self type.

r? `@estebank`

compiler/rustc_ast_lowering/src/path.rs

@@ -336,6 +336,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             insertion_sp,
                             suggestion,
                         );
+                        err.note("assuming a `'static` lifetime...");
                         err.emit();
                     }
                     AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {