c++: unifying constants vs their type [PR99186, PR104867]

c++: unifying constants vs their type [PR99186, PR104867]

When unifying constants we need to treat constants of different types
but same value as different in light of auto template parameters since
otherwise e.g. A<1> will unify with A<1u> (where A's template-head is
template<auto>).  This patch fixes this in a minimal way; it seems we
could get away with just using template_args_equal here, as we do in the
default case, or even just cp_tree_equal since the CONVERT_EXPR_P loop
seems to be dead code, but that's a simplification we could consider
during next stage 1.

	PR c++/99186
	PR c++/104867

gcc/cp/ChangeLog:

	* pt.cc (unify) <case INTEGER_CST>: Compare types as well.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1z/nontype-auto23.C: New test.
	* g++.dg/cpp1z/nontype-auto24.C: New test.