Auto merge of #53536 - RalfJung:array-drop, r=eddyb

fix array drop glue: properly turn raw ptr into reference

Discovered while working on https://github.com/rust-lang/rust/pull/53424: The generated drop glue uses an assignment `ptr = cur` where `ptr` is a reference and `cur` a raw pointer. This is not well-formed MIR.

Do we have MIR sanity checks that run on the drop glue and should have caught this?

r? @eddyb