cli: Add --video model.blob=on|off

Libvirt enables blob resources for the virtio video device since 9.2.0.
It accelerates the display path due to less or no copying of pixel data.

E.g.
  virt-install \
  ... \
  --video model.type=virtio,blob=on

It results in the following domain xml:

    <video>
      <model type="virtio" blob="on"/>
    </video>

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Lin Ma <lma@suse.de>

tests/data/cli/compare/virt-install-many-devices.xml

@@ -788,6 +788,11 @@
         <acceleration accel3d="yes"/>
       </model>
     </video>
+    <video>
+      <model type="virtio" blob="on">
+        <acceleration accel3d="yes"/>
+      </model>
+    </video>
     <hostdev mode="subsystem" type="pci" managed="yes">
       <source>
         <address domain="0" bus="0" slot="25" function="0"/>

tests/test_cli.py

@@ -752,6 +752,7 @@ source.reservations.managed=no,source.reservations.source.type=unix,source.reser
 --video cirrus
 --video model=qxl,vgamem=1,ram=2,vram=3,heads=4,accel3d=yes,vram64=65
 --video model=qxl,model.vgamem=1,model.ram=2,model.vram=3,model.heads=4,model.acceleration.accel3d=yes,model.vram64=65
+--video model=virtio,model.blob=on
 
 
 --smartcard passthrough,type=spicevmc

virtinst/cli.py

@@ -4664,6 +4664,7 @@ class ParserVideo(VirtCLIParser):
         cls.add_arg("model.vram", "vram")
         cls.add_arg("model.vram64", "vram64")
         cls.add_arg("model.vgamem", "vgamem")
+        cls.add_arg("model.blob", "blob")
 
 
 ###################

virtinst/devices/video.py

@@ -18,6 +18,7 @@ class DeviceVideo(Device):
     heads = XMLProperty("./model/@heads", is_int=True)
     vgamem = XMLProperty("./model/@vgamem", is_int=True)
     accel3d = XMLProperty("./model/acceleration/@accel3d", is_yesno=True)
+    blob = XMLProperty("./model/@blob", is_onoff=True)
 
     def _set_model(self, val):
         self._model = val