[Sema] Don't mark deleted special member functions as non-trivial

As noted in https://github.com/llvm/llvm-project/issues/59624, we sometimes mark implicitly
deleted special member functions as non-trivial. This is unnecessary work and leads to some
weird type traits errors.

This fixes the problem by making the implicitly deleted special member functions always
trivial.

Reviewed By: #clang-language-wg, erichkeane

Differential Revision: https://reviews.llvm.org/D140664