costly_bicon()

Created by: 9600bauds

Removes the bicon() icon caching which, at best, didn't work (fixes #11179 (closed)) Adds costly_bicon(). This is like bicon(), except it uses getFlatIcon(). Those who know anything about getFlatIcon() know that this means it should be used VERY SPARINGLY. I checked with PJB and he seemed to think it was OK to use this in the chemfridge, since the icon generation only happens once per pile and none of the things that go inside fridges will have many overlays and especially not overlays inside massive massive DMI files (the main thing that turns getFlatIcon() into performance hell).

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