Add new option for behavior when window on different desktop is activated

        
When a window that is on a different virtual desktop than the current one gets
activated, the current behavior is that the active virtual desktop will be switched
to the one the activated window is on. This may seem reasonable for a scenario where
the user explicitly intends to activate an existing window on a different desktop.
However, the following scenario is also (perhaps even more?) common: When an
application responds to a launch command by requesting to activate an existing
instance instead of opening a new one (such as Firefox or KDE System Settings), an
existing window on any desktop will get activated even when what the user had in
mind was opening a new window (on the desktop they are currently in). 

This means that opening an application, such as following a URL or accessing a
system setting, unexpectedly results in the user being teleported to a different
virtual desktop. This can be very irritating. The more expected behavior for these
users would be to have windows always open on the desktop where they are called
from. That's is what this commit adds as a new option.

BUG: 438375
FIXED-IN: 5.26