```rust
mod array {
    pub fn repeat<T: Clone, const N: usize>(value: T) -> [T; N];
}

impl [T; N] {
    pub fn resize<const NEW_LEN: usize>(self, value: T) -> [T; NEW_LEN] where T: Clone;
    pub fn resize_with<const NEW_LEN: usize>(self, mut f: impl FnMut() -> T) -> [T; NEW_LEN];
}
```

I tried to do `resize_with` as just
```rust
collect_into_array(IntoIter::new(self).chain(iter::repeat_with(f)))
```
but unfortunately that optimized very poorly.

As a result there's a bunch of refactoring in here to move the `Guard` struct that was previously private to `try_collect_into_array` over to its own module.  It's still very much internal -- it's visible only to the `core::array` module, with no intention of making this the anointed public thing.