Disable all `Behavior on` and `Transition` animations when global animation duration is zero

Otherwise weird things happen, such as https://bugs.kde.org/show_bug.cgi?id=483962.

Basically we need to make this change everywhere:

index 713b46946..2f29b7eaa 100644
--- desktoppackage/contents/explorer/AppletDelegate.qml
+++ desktoppackage/contents/explorer/AppletDelegate.qml
@@ -101,6 +101,7 @@ Item {
             Layout.alignment: Qt.AlignHCenter
             opacity: delegate.pendingUninstall ? 0.6 : 1
             Behavior on opacity {
+                enabled: Kirigami.Units.longDuration > 0
                 OpacityAnimator {
                     duration: Kirigami.Units.longDuration
                     easing.type: Easing.InOutQuad