Auto merge of #148425 - matthiaskrgr:rollup-pwibmxt, r=matthiaskrgr

Rollup of 3 pull requests

Successful merges:

 - rust-lang/rust#146260 (add SliceIndex wrapper types Last and Clamp<Idx>)
 - rust-lang/rust#148394 (Make explicit that `TypeId`'s layout and size are unstable)
 - rust-lang/rust#148402 (stdarch subtree update)

r? `@ghost`
`@rustbot` modify labels: rollup