Rollup merge of #152492 - biscuitrescue:fix-array-valtree-wf, r=BoxyUwU

mGCA: Enforce WF element types for array valtrees

Fixes rust-lang/rust#152125

Extends WellFormedness checking for const generics to validate that array element types in ValTrees match the declared element type.

### Problem
Before commit, this would have incorrectly compiled

``` rust
#![feature(adt_const_params, min_generic_const_args)]

use std::marker::ConstParamTy;

#[derive(Eq, PartialEq, ConstParamTy)]
struct Foo;

struct Bar;

fn foo<const N: [Foo; 1]>() {}

fn main() {
    foo::<{ [Bar] }>();
}
```

### Solution
Added a `ty::Array` arm to checking WellFormedness (similar to the existing `ty::Tuple` arm from rust-lang/rust#150713) which creates `ConstArgHasType` obligations for each array element, ensuring they match the array's declared element type.

I attempted to combine the `Tuple` and `Array` arms into a single arm, but this proved difficult due to pattern matching limitations, and the separate arm is more readable anyway.

### Tests

Added UI test which verifies that the type mismatch is now properly caught, and also returns an appropriate test message

r? @BoxyUwU

Author: JonathanBrouwer