Meta tracking issue for RFC 1892, "Deprecate uninitialized in favor of a new MaybeUninit type"

[Centril]

This issue tracks the progress of MaybeUninit<T> in general. The type was introduced in rust-lang/rfcs#1892. The old tracking issue is #53491.

This issue is not for discussion about specific extensions to MaybeUninit<T> and only exists to provide links to other places that track the progress of specific issues. If you wish to discuss some subject related to MaybeUninit<T>, please find an existing appropriate issue below or create an new issue and comment here with a link to the newly created issue.

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The MaybeUninit<T> related issues currently on deck are as follows:

• Tracking issue for uninitialized constructors for Box, Rc, Arc #63291; "Uninitialized constructors for Box, Rc, Arc"
• Tracking issue for RFC 2203, "Constants in array repeat expressions" #49147; "Constants in array repeat expressions"
• Tracking issue for #![feature(maybe_uninit_extra,const_maybe_uninit_write)] #63567; #![feature(maybe_uninit_extra)]
• Tracking issue for #![feature(maybe_uninit_ref)] #63568; #![feature(maybe_uninit_ref)]
• Tracking issue for #![feature(maybe_uninit_slice)] #63569; #![feature(maybe_uninit_slice)]
• Tracking issue for RFC 2582, &raw [mut | const] $place (raw_ref_op) #64490; &raw [mut | const] $place

Concerns:

• Fix incorrect use of MaybeUninit::assume_init_mut in flt2dec #76092

[scottmcm]

With MaybeUninit available on stable, we talked about this in lang backlog bonanza today and decided that we're good just closing this. There's lots more potential work, like new library APIs and more UB detection, but this meta-issue doesn't need to be open to track those things -- their own issues are sufficient.