Rollup merge of #112019 - jieyouxu:issue-111554, r=compiler-errors

Don't suggest changing `&self` and `&mut self` in function signature to be mutable when taking `&mut self` in closure

Current suggestion for when taking a mutable reference to `self` in a closure (as an upvar) will produce a machine-applicable suggestion to change the `self` in the function signature to `mut self`, but does not account for the specialness of implicit self in that it can already have `&` and `&mut` (see #111554). This causes the function signature to become `test(&mut mut self)` which does not seem desirable.

```
error[E0596]: cannot borrow `self` as mutable, as it is not declared as mutable
   --> src/sound_player.rs:870:11
    |
869 |     pub fn test(&mut self) {
    |                      ---- help: consider changing this to be mutable: `mut self`
870 |     || test2(&mut self);
    |              ^^^^^^^^^ cannot borrow as mutable
```

This PR suppresses the "changing this to be mutable" suggestion if the implicit self is either `ImplicitSelfKind::ImmRef` or `ImplicitSelfKind::MutRef`.

Fixes #111554.

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