Stabilize #![feature(non_null_from_ref)]

[mathisbot]

This PR stabilizes the following:

impl<T: ?Sized> NonNull<T> {
    pub const fn from_ref(reference: &T) -> NonNull<T>;
    pub const fn from_mut(reference: &mut T) -> NonNull<T>;
}

The feature is tracked in #130823.

[rustbot]

r? @tgross35

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[bjoernager]

Honest question: How can we stabilise this when FCP hasn't been voted through?

[bjoernager]

@rustbot label +T-libs-api -T-libs

r? libs-api