Rollup merge of #51396 - SimonSapin:option-nonzero-layout, r=SimonSapin
Rollup merge of #51396 - SimonSapin:option-nonzero-layout, r=SimonSapin

Make the size of Option<NonZero*> a documented guarantee.

Closes #49137, the tracking issue for `NonZero*`, as this was the last remaining open question.

Note that `ptr::NonNull<T>` already documents a similar guarantee.

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