[libc++] Fix `std::atomic::wait` ulock wait UL_COMPARE_AND_WAIT64 (#92783)

in `atomic::wait`, when we call the platform wait ulock_wait , we are
using UL_COMPARE_AND_WAIT. But we should use UL_COMPARE_AND_WAIT64
instead as the address we are waiting for is a 64 bit integer.

fixes https://github.com/llvm/llvm-project/issues/85107

It is rather hard to test directly because in `atomic::wait`, before
calling into the platform wait, our c++ code has some poll logic which
checks the value not changing. Thus in this patch, the test is using the
internal function.