ANDROID: KVM: arm64: Allow the hypervisor to snapshot the host stage-2 pagetables

Extend the hypervisor interface used for pagetable snapshotting. When 0 is
used as an argument for the snapshotting interface, the hypervisor
duplicates the host stage-2 pagetables. If no pages is given for the
region where we are about to store the snapshot, copy only the pagetable
configuration.

Bug: 260238318
Bug: 278749606
Change-Id: I2e1ac34bd842e352dbbeb7679cac0d62472af624
Signed-off-by: Sebastian Ene <sebastianene@google.com>