effects: Fix more animations

effects/overview: Fix animation of windows scaling back from a desktop bar

Due to nondeterministic nature of signal propagation in QML, changing both targetScale and state depending on dragHandler's activity could result in targetScale wrongly updating before the state change(and thus applied property changes and subsequent animated transition).

This fixes a bug when a window dragged to the top (but not onto another desktop) would animate its position back to its original position on a heap, but the scale would remain constant until the end of animation and only then rapidly jump back to a normally scaled state.

effects/private: Actually fade out minimized windows on exit

This is most likely just an oversight/omission from the times when the component was actively developed. There are five states total, including one for realtime interactions; four others need to be transitioned to.