Auto merge of #96979 - SabrinaJewson:waker-update, r=workingjubilee

Override `Waker::clone_from` to avoid cloning `Waker`s unnecessarily

This would be very useful for futures — I think it’s pretty much always what they want to do instead of `*waker = cx.waker().clone()`.

Tracking issue: rust-lang/rust#98287

r? rust-lang/libs-api `@rustbot` label +T-libs-api -T-libs