[libcxx] Make allocator<T>:allocate throw bad_array_new_length

Currently the member functions std::allocator<T>::allocate,
std::experimental::pmr::polymorphic_allocator::allocate and
std::resource_adaptor<T>::do_allocate throw an exception of type
std::length_error when the requested size exceeds the maximum size.

According to the C++ standard ([allocator.members]/4,
[mem.poly.allocator.mem]/1), std::allocator<T>::allocate and
std::pmr::polymorphic_allocator::allocate must throw a
std::bad_array_new_length exception in this case.

The patch fixes the issue with std::allocator<T>::allocate and changes
the type the exception thrown by
std::experimental::pmr::resource_adaptor<T>::do_allocate to
std::bad_array_new_length as well for consistency.

The patch resolves LWG 3237, LWG 3038 and LWG 3190.

Reviewed By: ldionne, #libc, Quuxplusone

Differential Revision: https://reviews.llvm.org/D110846