Auto merge of #115166 - Urgau:invalid_ref_casting-invalid-unsafecell-usage, r=est31

Lint on invalid usage of `UnsafeCell::raw_get` in reference casting

This PR proposes to take into account `UnsafeCell::raw_get` method call for non-Freeze types for the `invalid_reference_casting` lint.

The goal of this is to catch those kind of invalid reference casting:
```rust
fn as_mut<T>(x: &T) -> &mut T {
    unsafe { &mut *std::cell::UnsafeCell::raw_get(x as *const _ as *const _) }
    //~^ ERROR casting `&T` to `&mut T` is undefined behavior
}
```

r? `@est31`

compiler/rustc_span/src/symbol.rs

@@ -1639,6 +1639,7 @@ symbols! {
         unsafe_block_in_unsafe_fn,
         unsafe_cell,
         unsafe_cell_from_mut,
+        unsafe_cell_raw_get,
         unsafe_no_drop_flag,
         unsafe_pin_internals,
         unsize,