feat: add virtual desktop notification support

[amnweb]

This adds support for IVirtualDesktopNotification the COM interface Windows uses to push desktop change events instead of polling.

Pyvda currently has no way to get notified when desktops change, you have to poll. Windows exposes IVirtualDesktopNotification for exactly this.

Example:

from pyvda import VirtualDesktopNotificationService

class MyHandler:
    def desktop_changed(self, *args):
        print("switched!")
    def desktop_created(self, *args):
        print("new desktop")

svc = VirtualDesktopNotificationService()
cookie = svc.register(MyHandler())
# ...
svc.unregister(cookie)

Build coverage notification GUIDs and vtable layouts are defined for:

Win10 (< 20231)
Win11 21H2 (20231–22620)
Win11 23H2 (22621–22630)
Win11 23H2 b3085+ / 24H2 (22631+)
Tested on build 26200.8037 (25H2).