Auto merge of #53177 - nikomatsakis:nll-redundant-borrows-and-escaping-values, r...

Auto merge of #53177 - nikomatsakis:nll-redundant-borrows-and-escaping-values, r=pnkfelix

optimize redundant borrows and escaping paths in NLL

This builds on https://github.com/rust-lang/rust/pull/53168 and adds a commit that addresses https://github.com/rust-lang/rust/issues/53176 -- or at least I think it does. I marked this as WIP because I want to see the test results (and measure the performance). I also want to double check we're not adding in any unsoundness here.