KVM: selftests: arm64: Test vCPU-scoped feature ID registers

Test that CLIDR_EL1 and MPIDR_EL1 are modifiable from userspace and that
the values are preserved across a vCPU reset like the other feature ID
registers.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240502233529.1958459-8-oliver.upton@linux.dev


Signed-off-by: Marc Zyngier <maz@kernel.org>