Don't use forceActiveFocus to focus the applet toolbar

Generally, using forceActiveFocus is a bad thing since it indicates something is wrong in how focus is setup. It is also unnecessary here. PlasmoidHeading is a focus scope which means we can set whatever default focus we want inside it and then simply focus the heading to get our desired behaviour.

This also fixes the default focus behaviour as willShowOnActive is an async property and in this case is used too soon, before it is properly loaded.