Currently only the first created screenlock window gets focus.
On clicks, no focus events are sent, which makes it impossible to input
passwords. This patch now makes it possible to focus to a different
screenlock window (on a different monitor, for example) using a mouse
button press.
This should also fix newly created screenlock windows stealing the focus
of already displayed ones as only the first window gains automatic focus.
BUG: 348789
BUG: 374289