feat(console): one VNC console page, driven from the panel's bar

The VM page offered a lite and a full VNC console. Lite lacked a clipboard,
display settings and a way to reconnect; full put noVNC's own side bar under
the panel's bar, with a Fullscreen item that called a function noVNC does
not have, status messages hidden behind the bar, saved noVNC settings that
overrode the Access tab's, connection settings that cannot apply, and a
Connect button that reused the page's two-minute token and failed.

console-vnc.html and static/js/console_vnc.js replace both, on noVNC's RFB
with Bootstrap controls, and keep what the full view did:
- Status in the bar (Connecting, Connected, Disconnected, Connection lost,
  Could not connect, Authentication failed with the server's reason on
  hover); Disconnect, then Reconnect, which loads the page again for a new
  token.
- The VNC password in a dialog (with a username when the server asks for
  one), not a browser prompt; without passwordless console it is not in
  the page.
- Send key(s) gains Hold Ctrl / Alt / Windows (noVNC's extra keys).
- Clipboard: what the VM copies, sending text to the VM's clipboard, and
  typing it key by key (new: works in firmware, installers and login
  prompts; Shift for the characters a US keyboard shifts, 25 ms a key as
  firmware drops faster keys, verified in a UEFI shell).
- View: scaling (none, fit, resize the VM's screen), clip, drag a clipped
  screen, view only, dot cursor, quality, compression; it starts as
  Settings > Console says (a touch screen starts fitted).
- A Keyboard item on touch devices (noVNC's on-screen keyboard input,
  key events and Android's text-only input), Fullscreen with keyboard
  lock, the bell.
Dropped with the full view: noVNC's websocket host/port/path, repeater ID
and log level (the panel fixes them), automatic reconnect (the token is
single use in time), XVP power buttons (QEMU has no XVP) and shared-mode off.

The bar is compact (about 45 px in the 850x600 window). The Access tab has
one Console button instead of the Lite/Full split and four switches, and
it and the VM list open one window per VM (opening it again reloads it).

instances/tests/test_page_controls.py

@@ -84,7 +84,7 @@ class PageControls:
             return bool(doc.xpath("//form[@action=$a]", a=reverse(f"instances:{name}", args=[pk])))
 
         found = {
-            "console": bool(doc.xpath("//button[@id='consoleBtnGroup']")),
+            "console": bool(doc.xpath("//button[@id='console_button']")),
             "vv file": bool(doc.xpath("//a[@href=$a]", a=reverse("instances:getvvfile", args=[pk]))),
             "vdi": bool(doc.xpath("//*[@id='vdiconsole']")),
             "power": form("poweroff") or form("poweron"),