impl `Default` for `array::IntoIter` cc rust-lang/rust#91583 my personal use of this feature comes from https://github.com/fee1-dead/w/blob/092db5df631ea515b688bae99c7f02eef12d7221/src/cont.rs#L154-L170 insta-stable, but I feel like this is small enough to _not_ require an ACP (but a FCP per https://forge.rust-lang.org/libs/maintaining-std.html#when-theres-new-trait-impls)? feel free to correct me if I am wrong.