Auto merge of #120730 - estebank:confusable-api, r=oli-obk

Provide suggestions through `rustc_confusables` annotations

Help with common API confusion, like asking for `push` when the data structure really has `append`.

```
error[E0599]: no method named `size` found for struct `Vec<{integer}>` in the current scope
  --> $DIR/rustc_confusables_std_cases.rs:17:7
   |
LL |     x.size();
   |       ^^^^
   |
help: you might have meant to use `len`
   |
LL |     x.len();
   |       ~~~
help: there is a method with a similar name
   |
LL |     x.resize();
   |       ~~~~~~
```

Fix #59450 (we can open subsequent tickets for specific cases).

Fix #108437:

```
error[E0599]: `Option<{integer}>` is not an iterator
   --> f101.rs:3:9
    |
3   |     opt.flat_map(|val| Some(val));
    |         ^^^^^^^^ `Option<{integer}>` is not an iterator
    |
   ::: /home/gh-estebank/rust/library/core/src/option.rs:571:1
    |
571 | pub enum Option<T> {
    | ------------------ doesn't satisfy `Option<{integer}>: Iterator`
    |
    = note: the following trait bounds were not satisfied:
            `Option<{integer}>: Iterator`
            which is required by `&mut Option<{integer}>: Iterator`
help: you might have meant to use `and_then`
    |
3   |     opt.and_then(|val| Some(val));
    |         ~~~~~~~~
```

On type error of method call arguments, look at confusables for suggestion. Fix #87212:

```
error[E0308]: mismatched types
    --> f101.rs:8:18
     |
8    |     stuff.append(Thing);
     |           ------ ^^^^^ expected `&mut Vec<Thing>`, found `Thing`
     |           |
     |           arguments to this method are incorrect
     |
     = note: expected mutable reference `&mut Vec<Thing>`
                           found struct `Thing`
note: method defined here
    --> /home/gh-estebank/rust/library/alloc/src/vec/mod.rs:2025:12
     |
2025 |     pub fn append(&mut self, other: &mut Self) {
     |            ^^^^^^
help: you might have meant to use `push`
     |
8    |     stuff.push(Thing);
     |           ~~~~
```

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2929,7 +2929,7 @@ define_print_and_forward_display! {
 
     ty::ExistentialTraitRef<'tcx> {
         // Use a type that can't appear in defaults of type parameters.
-        let dummy_self = Ty::new_fresh(cx.tcx(),0);
+        let dummy_self = Ty::new_fresh(cx.tcx(), 0);
         let trait_ref = self.with_self_ty(cx.tcx(), dummy_self);
         p!(print(trait_ref.print_only_trait_path()))
     }