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.

compiler/rustc_trait_selection/src/lib.rs

@@ -11,7 +11,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(array_value_iter)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(drain_filter)]