[ADT] Fix Optional<> with llvm::is_trivially_move_constructible

Fix the compatibility of Optional<> with some GCC versions that it will fail
to compile when T is getting checked for `is_trivially_move_constructible`
as mentioned here: https://reviews.llvm.org/D93510#2538983

Fix the problem by using `llvm::is_trivially_move_constructible`.

Reviewed By: jplayer-nv, tatyana-krasnukha

Differential Revision: https://reviews.llvm.org/D117254