kubevirt_vm: Use {Instancetype,Preference}Matchers

Use InstancetypeMatchers and PreferenceMatchers directly instead of
providing multiple arguments to prevent unnecessary abstraction.

Signed-off-by: Felix Matouschek <fmatouschek@redhat.com>

examples/play-create.yml

@@ -7,8 +7,10 @@
         namespace: default
         labels:
           app: test
-        instancetype: u1.medium
-        preference: fedora
+        instancetype:
+          name: u1.medium
+        preference:
+          name: fedora
         interfaces:
         - name: default
           masquerade: {}