feat(instances): a VM's console settings in two cards, with a password action

Settings > Console was one horizontal form, and on a running VM its
Update button was disabled. The owner chose this layout from three
rendered options: the console type on top, then a "VNC connection" card
(listen address, keymap) and a "VNC password" card.

- The password is changed by an action: keep it, generate a new one,
  set a new one or remove it. This replaces the Generate and Clear
  boxes and their precedence, and an emptied field no longer removes
  the password silently. The pane says whether a password is set; the
  form no longer carries the password itself.
- A VNC password takes at most 8 bytes: libvirt refuses a longer one
  ("VNC password is 9 characters long, only 8 permitted"). Generate and
  a new VM's random password now make 8 characters; they made 12, which
  libvirt 11 refuses. A set password keeps its spaces.
- Every check is in the form, so a refused save changes nothing; before,
  a refused password removal still saved the other settings.
- The settings can be saved while the VM runs: they are in the
  persistent definition. A line says the running console keeps its
  settings until the VM is shut down and started.
- The console type shown and compared is the persistent one; it was the
  running VM's, so a pending switch to Serial showed VNC and a later
  save could switch again.
- While the saved type is Serial, the VNC settings are not shown or
  taken; choosing Serial ignores the posted VNC settings.

vrtManager/instance.py

@@ -1530,14 +1530,11 @@ class wvmInstance(wvmConnect):
         socket = util.get_xml_path(self._XMLDesc(0), "/domain/devices/graphics/@socket")
         return socket
 
-    def get_console_type(self):
-        console_type = util.get_xml_path(
-            self._XMLDesc(0), "/domain/devices/graphics/@type"
-        )
+    def get_console_type(self, config=False):
+        xml = self._XMLDesc(PERSISTENT_XML if config else 0)
+        console_type = util.get_xml_path(xml, "/domain/devices/graphics/@type")
         if console_type is None:
-            console_type = util.get_xml_path(
-                self._XMLDesc(0), "/domain/devices/console/@type"
-            )
+            console_type = util.get_xml_path(xml, "/domain/devices/console/@type")
         return console_type
 
     def get_console_port(self, console_type=None):