Rollup merge of #83092 - petrochenkov:qspan, r=estebank

More precise spans for HIR paths

`Ty::assoc_item` is lowered to `<Ty>::assoc_item` in HIR, but `Ty` got span from the whole path.
This PR fixes that, and adjusts some diagnostic code that relied on `Ty` having the whole path span.

This is a pre-requisite for https://github.com/rust-lang/rust/pull/82868 (we cannot report suggestions like `Tr::assoc` -> `<dyn Tr>::assoc` with the current imprecise spans).
r? ````@estebank````

compiler/rustc_hir/src/hir.rs

@@ -1809,7 +1809,7 @@ impl<'hir> QPath<'hir> {
     pub fn span(&self) -> Span {
         match *self {
             QPath::Resolved(_, path) => path.span,
-            QPath::TypeRelative(_, ps) => ps.ident.span,
+            QPath::TypeRelative(qself, ps) => qself.span.to(ps.ident.span),
             QPath::LangItem(_, span) => span,
         }
     }