KVM: selftests: Add test for AArch32 ID registers

Add a test to assert that KVM handles the AArch64 views of the AArch32
ID registers as RAZ/WI (writable only from userspace). For registers
that were already hidden or unallocated, expect RAZ + invariant
behavior.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220913094441.3957645-8-oliver.upton@linux.dev