Allow activating windows on other desktops regardless of focus stealing protection

Currently, on X11, when activating a window that is not on the current desktop we allow this
only if focus stealing protection is set to none.

If any focus stealing protection is set then activation is denied. That behavior is
unintiutive to the user. When I e.g. click on a notification from a chat app I expect
something to happen, regardless of focus stealing protection.

Remove the special handling of windows on different desktops and only apply the usual
focus stealing prevention checks (based on timestamps etc). This also matches the behavior
on Wayland.