Auto merge of #116330 - RalfJung:dont-key-on-allocid, r=oli-obk

remove Key impls for types that involve an AllocId

I don't understand how but somehow that leads to issues like rust-lang/rust#83085? Anyway removing unused impls doesn't seem like a bad idea. The concerning part is that of course nothing will stop us from having such impls again in the future, alongside re-introducing bugs like #83085.

r? `@oli-obk`