BUG: 398975
FIXED-IN: 5.53
Use a red X instead of a dash in all off and muted icons for consistency as well as small tweaks with the placement in the `mic-off` iconsstrikethrough version of a neutral icon for `*-off` icons and a red circle with a diagonal line for `*-muted` icons. Also add `22px` `audio-{on,off,ready}` while we're at it.