Auto merge of #139088 - spastorino:ergonomic-ref-counting-2, r=nikomatsakis

Ergonomic ref counting: optimize away clones when possible

This PR build on top of rust-lang/rust#134797. It optimizes codegen of ergonomic ref-counting when the type being `use`d is only known to be copy after monomorphization. We avoid codening a clone and generate bitwise copy instead.

RFC: rust-lang/rfcs#3680
Tracking issue: rust-lang/rust#132290
Project goal: rust-lang/rust-project-goals#107

r? `@nikomatsakis`

This PR could better sit on top of rust-lang/rust#131650 but as it did not land yet I've decided to just do minimal changes. It may be the case that doing what I'm doing regress the performance and we may need to go the full route of rust-lang/rust#131650.
cc `@saethlin` in this regard.

Author: bors