Apply std::move to predicate/comparator-like entities

[dmitriy-sobolev]

I guess, even without having capture list we could benefit from using std::move(__comp) and std::move(__proj).

Originally posted by @rarutyun in #1471 (comment)

[akukanov]

Are not the predicates, comparators etc. in modern C++supposed to be very lightweight objects passed by values? What benefits of moving those are expected, especially "even without having capture list"?