[libc++] Add hide_from_abi check for classes

We already have a clang-tidy check for making sure that `_LIBCPP_HIDE_FROM_ABI` is on free functions. This patch extends this to class members. The places where we don't check for `_LIBCPP_HIDE_FROM_ABI` are classes for which we have an instantiation in the library.

Reviewed By: ldionne, Mordante, #libc

Spies: jplehr, mikhail.ramalho, sstefan1, libcxx-commits, krytarowski, miyuki, smeenai

Differential Revision: https://reviews.llvm.org/D142332