Auto merge of #53571 - MaloJaffre:vecdeque-emergency, r=RalfJung
Auto merge of #53571 - MaloJaffre:vecdeque-emergency, r=RalfJung

Fix unsoundness for VecDeque

 See individual commit for more details.

r? @RalfJung.

Fixes https://github.com/rust-lang/rust/issues/53566, fixes https://github.com/rust-lang/rust/issues/53529

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