Update tests

Extend to other operations

Refractor check in a separate function

Fix more tests

Token normalization is merged directly into `bump`.
Special "unknown macro variable" diagnostic for unexpected `$`s is removed as preventing legal code from compiling.

They are always set synchronously with normalized tokens now

Always const qualify literals by type

r? @eddyb

…=ecstatic-morse

Select an appropriate unused lifetime name in suggestion

Follow up to rust-lang#69048.

…henkov

parse: fuse associated and extern items up to defaultness

Language changes:

- The grammar of extern `type` aliases is unified with associated ones, and becomes:
  ```rust
  TypeItem = "type" ident generics {":" bounds}? where_clause {"=" type}? ";" ;
  ```

  Semantic restrictions (`ast_validation`) are added to forbid any parameters in `generics`, any bounds in `bounds`, and any predicates in `where_clause`, as well as the presence of a type expression (`= u8`).

  (Work still remains to fuse this with free `type` aliases, but this can be done later.)

- The grammar of constants and static items (free, associated, and extern) now permits the absence of an expression, and becomes:

  ```rust
  GlobalItem = {"const" {ident | "_"} | "static" "mut"? ident} {"=" expr}? ";" ;
  ```

  - A semantic restriction is added to enforce the presence of the expression (the body).
  - A semantic restriction is added to reject `const _` in associated contexts.

Together, these changes allow us to fuse the grammar of associated items and extern items up to `default`ness which is the main goal of the PR.

-----------------------

We are now very close to fully fusing the entirely of item parsing and their ASTs. To progress further, we must make a decision: should we parse e.g. `default use foo::bar;` and whatnot? Accepting that is likely easiest from a parsing perspective, as it does not require using look-ahead, but it is perhaps not too onerous to only accept it for `fn`s (and all their various qualifiers), `const`s, `static`s, and `type`s.

r? @petrochenkov

parser: Simplify treatment of macro variables in `Parser::bump`

Follow-up to rust-lang#69006.

Token normalization for `$ident` and `$lifetime` is merged directly into `bump`.
Special "unknown macro variable" diagnostic for unexpected `$`s is removed as preventing legal code from compiling (as a result `bump` also doesn't call itself recursively anymore and can't make `prev_token` inconsistent).

r? @Centril

…, r=estebank

Do not emit note suggesting to implement operation trait to foreign type

When a binary operation isn't valid, you will get a lint proposing to add a trait implementation to make the operation possible. However, this cannot be done for foreign types, such as types from `core` or `std`.

For example:
```
= note: an implementation of `std::ops::Add` might be missing for `std::option::Option<i8>`
```
As mentioned in rust-lang#60497 (comment):
> The note suggesting implementing Add<i8> should only be emitted if Option<i8> were local to the current crate, which it isn't, so in this case it shouldn't be emitted.

(I will use the CI to check tests for me, or my computer will just burn... and running IDEs is not possible on a pile of ashes)

r? @estebank

…stebank

parse: recover `mut (x @ y)` as `(mut x @ mut y)`.

Follow up to rust-lang#68992 (comment) and rust-lang#63945.

Specifically, when given `let mut (x @ y)` we recover with `let (mut x @ mut y)` as the suggestion:

```rust
error: `mut` must be attached to each individual binding
  --> $DIR/mut-patterns.rs:12:9
   |
LL |     let mut (x @ y) = 0;
   |         ^^^^^^^^^^^ help: add `mut` to each binding: `(mut x @ mut y)`
   |
   = note: `mut` may be followed by `variable` and `variable @ pattern`
```

r? @matthewjasper @estebank