Align ArrayWindows trait impls with Windows

[cuviper]

With slice::ArrayWindows getting ready to stabilize in 1.94, I noticed that it currently has some differences in trait implementations compared to slice::Windows, and I think we should align these.

• Remove derive(Copy) -- we generally don't want Copy for iterators at all, as this is seen as a footgun (e.g. remove Copy impls from remaining iterators #21809). This is obviously a breaking change though, so we should only remove this if we also backport the removal before it's stable. Otherwise, it should at least be replaced by a manual impl without requiring T: Copy.
• Manually impl Clone, simply to avoid requiring T: Clone.
• impl FusedIterator, because it is trivially so. The since = "1.94.0" assumes we'll backport this, otherwise we should change that to the "current" placeholder.
• impl TrustedLen, because we can trust our implementation.
• impl TrustedRandomAccess, because the required __iterator_get_unchecked method is straightforward.

r? libs-api

@rustbot label beta-nominated
(at least for the Copy removal, but we could be more selective about the rest).