vhost-iova-tree, svq: Implement GPA->IOVA & partial IOVA->HVA trees

vhost-iova-tree, svq: Implement GPA->IOVA & partial IOVA->HVA trees

Creates and supports a GPA->IOVA tree and a partial IOVA->HVA tree by
splitting up guest-backed memory maps and host-only memory maps from the
full IOVA->HVA tree. That is, any guest-backed memory maps are now
stored in the GPA->IOVA tree and host-only memory maps stay in the
IOVA->HVA tree.

Also propagates the GPAs (in_addr/out_addr) of a VirtQueueElement to
vhost_svq_translate_addr() to translate GPAs to IOVAs via the GPA->IOVA
tree (when descriptors are backed by guest memory). For descriptors
backed by host-only memory, the existing partial SVQ IOVA->HVA tree is
used.

GPAs are unique in the guest's address space, ensuring unambiguous IOVA
translations. This avoids the issue where different GPAs map to the same
HVA, causing the original HVA->IOVA translation to potentially return an
IOVA associated with the wrong intended GPA.

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20250217144936.3589907-3-jonah.palmer@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>