[css-box-4] Audit boxes #10121
Description
This spec defines several different sets of boxes, but maybe not all of the necessary ones; e.g. transform-box and box-sizing don't include padding-box, and there's no set for that.
We should check the uses of the various box types to make sure they're subsetting what they want to subset, and that we have the appropriate subsets available if that's warranted.