Auto merge of #141731 - compiler-errors:tweak-fast-path-trait, r=lcnr

Tweak fast path trait handling

(1.) Make it more sound by considering polarity (lol)

(2.) Make it more general, by considering higher-ranked size/copy/clone

(2.) Make it less observable, by only doing copy/clone fast path if there are no regions involved

r? lcnr

Author: bors