Rollup merge of #87447 - RalfJung:not-null, r=oli-obk
Rollup merge of #87447 - RalfJung:not-null, r=oli-obk

Miri: santiy check that null pointer can never have an AllocId

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust