Rollup merge of #124908 - saethlin:ref-casting_bigger_place_projection, r=fee1-dead

Handle field projections like slice indexing in invalid_reference_casting

r? `@Urgau`

I saw the implementation in https://github.com/rust-lang/rust/pull/124761, and I was wondering if we also need to handle field access. We do. Without this PR, we get this errant diagnostic:
```
error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
  --> /home/ben/rust/tests/ui/lint/reference_casting.rs:262:18
   |
LL |         let r = &mut v.0;
   |                      --- backing allocation comes from here
LL |         let ptr = r as *mut i32 as *mut Vec3<i32>;
   |                   ------------------------------- casting happend here
LL |         unsafe { *ptr = Vec3(0, 0, 0) }
   |                  ^^^^^^^^^^^^^^^^^^^^
   |
   = note: casting from `i32` (4 bytes) to `Vec3<i32>` (12 bytes)
```