Avoid refreshing all layout when removing/adding items in list.

Use default video conference layout when making a call. Fix active speaker device on GUI initialization (going from/to fullscreen, opening new call window). Changing sort heuristics on participant devices to stabilized stickers: Ignore time of joining and keep only the order of the list of participants. Display the preview at the end of the list. In active speaker : Replace the layout refresh workaround by moving the top margin on participant list. This avoid to reload camera each time.

TODO: update SDK to retrieve the correct order of participant devices.