Auto merge of #71274 - RalfJung:raw-init-check-aggregate, r=petrochenkov

might_permit_raw_init: also check aggregate fields

This is the next step for https://github.com/rust-lang/rust/issues/66151: when doing `mem::zeroed`/`mem::uninitialized`, also recursively check fields of aggregates (except for arrays) for whether they permit zero/uninit initialization.