This implements better active window synchronization between Wine and X11 by requesting _NET_ACTIVE_WINDOW change whenever the Win32 active window changes, using source = 2 (pager) which is more often obeyed than other source values by the window managers.
This also implements SWP_NOACTIVATE properly by setting _NET_WM_USER_TIME time to 0 before mapping a window, which has the correct semantics, while later sending _NET_ACTIVE_WINDOW to activate it if it ends up being necessary to match the Win32 logic.
-- v2: winex11: Use _NET_ACTIVE_WINDOW to request/track window activation. win32u: Call ActivateWindow callback when foreground window changes. win32u: Return foreground window changes from GetWindowStateUpdates. winex11: Refactor X11DRV_GetWindowStateUpdates control flow. winex11: Keep track of whether mapped window needs activation. winex11: Only set focus_time_prop for managed windows.