We can't get all the way there because we can't create pads outside
of modules and the Gerbers don't store any grouping/footprint info.
This change moves us from outputing a via for every flashed item
(some of which don't even have holes) to synthesizing pads from
flashed items using a via (when they have holes) and a copper polygon.
This is much better for SMD pads, perhaps better for regular pads,
and no worse for vias.
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