mem_sharing: VM forking

mem_sharing: VM forking

VM forking is the process of creating a domain with an empty memory space and a
parent domain specified from which to populate the memory when necessary. For
the new domain to be functional the VM state is copied over as part of the fork
operation (HVM params, hap allocation, etc).

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>