Auto merge of #25035 - Stebalien:iter, r=aturon

Specifically, make count, nth, and last call the corresponding methods on the underlying iterator where possible. This way, if the underlying iterator has an optimized count, nth, or last implementations (e.g. slice::Iter), these methods will propagate these optimizations.

Additionally, change Skip::next to take advantage of a potentially optimized nth method on the underlying iterator.

This covers:

* core::iter::Chain: count, last, nth
* core::iter::Enumerate: count, nth
* core::iter::Peekable: count, last, nth
* core::iter::Skip: count, last, next (should call nth), nth
* core::iter::Take: nth
* core::iter::Fuse: count, last, nth

of #24214.

0 files changed, 0 insertions, 0 deletions