Kwin: double-click on left icon closes window mode: reduce need to keep left button pressed down for 2 seconds to show menu

[star-buck]

currently one must hold the left mouse button down for about 2 seconds before window-options popup appears. could be changed that the first click triggers to show the menu after ~0.5 second delay if no second click occurs before that to close the window.

[kbroulik]

https://phabricator.kde.org/D10855