Auto merge of #114811 - estebank:impl-ambiguity, r=wesleywiser

Show more information when multiple `impl`s apply

- When there are `impl`s without type params, show only those (to avoid showing overly generic `impl`s).
```
error[E0283]: type annotations needed
  --> $DIR/multiple-impl-apply.rs:34:9
   |
LL |     let y = x.into();
   |         ^     ---- type must be known at this point
   |
note: multiple `impl`s satisfying `_: From<Baz>` found
  --> $DIR/multiple-impl-apply.rs:14:1
   |
LL | impl From<Baz> for Bar {
   | ^^^^^^^^^^^^^^^^^^^^^^
...
LL | impl From<Baz> for Foo {
   | ^^^^^^^^^^^^^^^^^^^^^^
   = note: required for `Baz` to implement `Into<_>`
help: consider giving `y` an explicit type
   |
LL |     let y: /* Type */ = x.into();
   |          ++++++++++++
```

- Lower the importance of `T: Sized`, `T: WellFormed` and coercion errors, to prioritize more relevant errors. The pre-existing deduplication logic deals with hiding redundant errors better that way, and we show errors with more metadata that is useful to the user.

- Show `<SelfTy as Trait>::assoc_fn` suggestion in more cases.
```
error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
  --> $DIR/cross-return-site-inference.rs:38:16
   |
LL |     return Err(From::from("foo"));
   |                ^^^^^^^^^^ cannot call associated function of trait
   |
help: use a fully-qualified path to a specific available implementation
   |
LL |     return Err(</* self type */ as From>::from("foo"));
   |                +++++++++++++++++++     +
```

Fix #88284.

Author: bors

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -368,7 +368,7 @@ fn check_opaque_type_well_formed<'tcx>(
     if errors.is_empty() {
         Ok(definition_ty)
     } else {
-        Err(infcx.err_ctxt().report_fulfillment_errors(&errors))
+        Err(infcx.err_ctxt().report_fulfillment_errors(errors))
     }
 }
 

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -743,7 +743,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
                 let errors = ocx.select_all_or_error();
                 if !errors.is_empty() {
-                    infcx.err_ctxt().report_fulfillment_errors(&errors);
+                    infcx.err_ctxt().report_fulfillment_errors(errors);
                 }
 
                 // Attempting to call a trait method?