core: removed limitation of get topSizeVms query

Use a new query to display vms (with disks and snapshots) in Storage main
tab-VMs sub tab. Removed the previously used query
GetTopSizeVmsFromStorageDomain.
Also, clean unused usages of the old query in REST and UI and added test
for the new query.

Change-Id: Ia44f746a9321282fa99c7a11de92e720e3e0c610
Signed-off-by: Alissa Bonas <abonas@redhat.com>
Signed-off-by: Allon Mureinik <amureini@redhat.com>