lookingGlass: Clean up the stylesheet and improve visuals overall

lookingGlass: Clean up the stylesheet and improve visuals overall

- shuffle stylesheet around for readability
- change names and classes of elements to be consistent
- added style classes to window list elements so they can be styled
- make sure all elements follow OSD style even in light theme
- clean out some old styles

Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/7746
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3412>