Partially revert a0c4a8e7

Unfortunately, a0c4a8e7 has a major bug
where clients that track focus events may get confused by focusToNull().

One such a notable example is Dota 2. It tracks the focus events to
minimize itself after the keyboard focus has been lost as well stop
playing music while it's in background. So, when we call focusToNull(),
Dota 2 will receive a corresponding FocusOut event and ask the window
manager to minimize it. It doesn't really matter that the FocusOut
event is going to be followed by a FocusIn event because when a window
is minimized, kwin will activate the next one in the focus chain.

Since those issues can't be fixed from the window manager's side, this
patch partially reverts a0c4a leaving only the autotest.

BUG: 424223
FIXED-IN: 5.19.4


(cherry picked from commit 27172528)