c++/c-common: Fix convert_vector_to_array_for_subscript for qualified vector types...

c++/c-common: Fix convert_vector_to_array_for_subscript for qualified vector types [PR89224]

After r7-987-gf17a223de829cb, the access for the elements of a vector type would lose the qualifiers.
So if we had `constvector[0]`, the type of the element of the array would not have const on it.
This was due to a missing build_qualified_type for the inner type of the vector when building the array type.
We need to add back the call to build_qualified_type and now the access has the correct qualifiers. So the
overloads and even if it is a lvalue or rvalue is correctly done.

Note we correctly now reject the testcase gcc.dg/pr83415.c which was incorrectly accepted after r7-987-gf17a223de829cb.

Built and tested for aarch64-linux-gnu.

	PR c++/89224

gcc/c-family/ChangeLog:

	* c-common.cc (convert_vector_to_array_for_subscript): Call build_qualified_type
	for the inner type.

gcc/cp/ChangeLog:

	* constexpr.cc (cxx_eval_array_reference): Compare main variants
	for the vector/array types instead of the types directly.

gcc/testsuite/ChangeLog:

	* g++.dg/torture/vector-subaccess-1.C: New test.
	* gcc.dg/pr83415.c: Change warning to error.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
(cherry picked from commit 4421d35167b3083e0f2e4c84c91fded09a30cf22)