Fixes #6783, moves spacesuits to a separate file

Adds an update_clothing_icon() proc to clothing items that will call the relevant icon update proc on the mob which is equipping the clothing, if any. Changes various clothing procs to not call update icon procs on usr
which may not even be the mob wearing the clothing.

I can't think of many good reasons why icon update procs should be called on ```usr``` when updating the appearance of worn items. Sure, for some clothing procs ```usr``` will happen to be the mob actually wearing the clothing, but should the verb ever become callable by anyone not wearing the clothing (like if buttoning someone else's labcoat ever becomes possible) the code will no longer work as intended, from what I understand. Also it seems like it can confuse people who don't seem to understand ```usr```, like whichever poor soul wrote emp_act() for the chameleon suit.