In terms of how much junk we send users, have around, etc. Clean that up, yo.

• T230664: Use css classes for things instead of just duplicating everything everywhere with mixins - cripes
• Redundant overrides in terms of css, etc, break that up and block things together with shared definitions
• Do we actually need png fallbacks for most of the svgs (js-only stuff, we definitely don't because js browsers all support svg; flex requiring stuff? etc)
• Insane code junk, do we really need a custom category parser, etc, can we just assume 'actions' are 'page tools' and be done with it, etc