Stabilize by-value [T; N] iterator core::array::IntoIter

Tracking issue: https://github.com/rust-lang/rust/issues/65798

This is unblocked now that `min_const_generics` has been stabilized
in https://github.com/rust-lang/rust/pull/79135.

This PR does *not* include the corresponding `IntoIterator` impl,
which is https://github.com/rust-lang/rust/pull/65819.
Instead, an iterator can be constructed through the `new` method.

`new` would become unnecessary when `IntoIterator` is implemented
and might be deprecated then, although it will stay stable.

library/core/src/array/mod.rs

@@ -17,7 +17,7 @@ use crate::slice::{Iter, IterMut};
 
 mod iter;
 
-#[unstable(feature = "array_value_iter", issue = "65798")]
+#[stable(feature = "array_value_iter", since = "1.51.0")]
 pub use iter::IntoIter;
 
 /// Converts a reference to `T` into a reference to an array of length 1 (without copying).