c++: Handle RAW_DATA_CST in unify [PR118390]

This patch uses the count_ctor_elements function to fix up
unify deduction of array sizes.

2025-01-15  Jakub Jelinek  <jakub@redhat.com>

	PR c++/118390
	* cp-tree.h (count_ctor_elements): Declare.
	* call.cc (count_ctor_elements): No longer static.
	* pt.cc (unify): Use count_ctor_elements instead of
	CONSTRUCTOR_NELTS.

	* g++.dg/cpp/embed-20.C: New test.
	* g++.dg/cpp0x/pr118390.C: New test.