Rollup merge of #63215 - gnzlbg:patch-6, r=Centril
Rollup merge of #63215 - gnzlbg:patch-6, r=Centril

Clarify semantics of mem::zeroed

Clarifies the semantics of `mem::zeroed`.

r? @Centril

cc @RalfJung

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