Auto merge of #89769 - jkugelman:must-use-maybe-uninit-new, r=joshtriplett
Auto merge of #89769 - jkugelman:must-use-maybe-uninit-new, r=joshtriplett

Add #[must_use] to MaybeUninit::new

As discussed in https://github.com/rust-lang/rust/pull/89729#issuecomment-939775659.

Parent issue: #89692

r? `@joshtriplett`

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