Auto merge of #42396 - venkatagiri:remove_lifetime_extn, r=arielb1

rustc: remove temporary lifetime extension by borrow hint

closes #39283.

Thanks to @nikomatsakis for mentoring on this one.

r? @arielb1

diff --cc src/librustc/middle/expr_use_visitor.rs
Simple merge

diff --cc src/librustc_borrowck/borrowck/mod.rs
Simple merge

diff --cc src/librustc_typeck/check/regionck.rs
Simple merge