Auto merge of #111567 - Urgau:uplift_cast_ref_to_mut, r=b-naber

Uplift `clippy::cast_ref_to_mut` lint

This PR aims at uplifting the `clippy::cast_ref_to_mut` lint into rustc.

## `cast_ref_to_mut`

(deny-by-default)

The `cast_ref_to_mut` lint checks for casts of `&T` to `&mut T` without using interior mutability.

### Example

```rust,compile_fail
fn x(r: &i32) {
    unsafe {
        *(r as *const i32 as *mut i32) += 1;
    }
}
```

### Explanation

Casting `&T` to `&mut T` without interior mutability is undefined behavior, as it's a violation of Rust reference aliasing requirements.

-----

Mostly followed the instructions for uplifting a clippy lint described here: rust-lang/rust#99696 (review)

`@rustbot` label: +I-lang-nominated
r? compiler

-----

For Clippy:

changelog: Moves: Uplifted `clippy::cast_ref_to_mut` into rustc

tests/fail/modifying_constants.rs

@@ -1,6 +1,8 @@
 // This should fail even without validation/SB
 //@compile-flags: -Zmiri-disable-validation -Zmiri-disable-stacked-borrows
 
+#![allow(cast_ref_to_mut)]
+
 fn main() {
     let x = &1; // the `&1` is promoted to a constant, but it used to be that only the pointer is marked static, not the pointee
     let y = unsafe { &mut *(x as *const i32 as *mut i32) };

tests/fail/stacked_borrows/shr_frozen_violation1.rs

@@ -1,3 +1,5 @@
+#![allow(cast_ref_to_mut)]
+
 fn foo(x: &mut i32) -> i32 {
     *x = 5;
     unknown_code(&*x);