Show note for type ascription on a local binding interpreted as a constant pattern and not a new variable
Given the code
```rust
pub fn main() {
const y: i32 = 4;
let y: i32 = 3;
}
```
`y` in the let binding is actually interpreted as a constant pattern and is not a new variable, causing confusing diagnostics about refutable patterns in local binding.
This PR extends the note for type ascription of a constant pattern to `AscribeUserType` patterns which have `Constant` subpatterns.
Fixes#112269.
e4106065bf