[libc++] Benchmark non-trivial types for the copy/move family of algorithms

[ldionne]

For the copy family of algorithms I think it would be interesting to test some non-trivial type. Specifically, that the compiler would not be able to see through the operation. That could be achieved by an out-of-line definition or a [[gnu::noinline]] on the function. Maybe just an optimization barrier would work to.

Originally posted by @philnik777 in #127354 (comment)