Draft: Thumbnail size changed

• From 64 to 2048 thumbnail sizes, only powers of 2 (default to 512).
• This MR was created because screens have high resolution now.
• src/nautilus-thumbnails.c: get_thumbnail_factory too small thumbnails with video files is fixed
• I dont like the display scale factor but if we have an app level similar setting or if we should create one, let me know
• I am disappointed by the fact that the sidebar removal dont work anymore (but I will probably remove it only in my fork)
• Because too much space is wasted I will implement 16/9 thumbnail ratio in my fork that I wont push (unless people interested)

TODO:

• I need help to access the zoom level/icon size member to not force highest thumnail resolution.
• Can somebody explain why max_thumbnail_size computation was so complex?

requires: gnome-desktop!161 (closed) (to fix CI)