Auto merge of #105545 - erikdesjardins:ptrclean, r=bjorn3

cleanup: remove pointee types

This can't be merged until the oldest LLVM version we support uses opaque pointers, which will be the case after #114148. (Also note `-Cllvm-args="-opaque-pointers=0"` can technically be used in LLVM 15, though I don't think we should support that configuration.)

I initially hoped this would provide some minor perf win, but in rust-lang/rust#105412 (comment) it had very little impact, so this is only valuable as a cleanup.

As a followup, this will enable #96242 to be resolved.

r? `@ghost`

`@rustbot` label S-blocked