Parse type const syntax

- https://github.com/rust-lang/rust/issues/132980

Example: https://github.com/rust-lang/rust/blob/d39561c2d2b55985d3b6331cc52403e038e7fc8b/tests/debuginfo/associated-const-bindings.rs#L16-L21

```rust
trait Trait {
    type const N: usize;
}
impl Trait for () {
    type const N: usize = 101;
}
```