fixes modsuit icons (#71998)

## About The Pull Request
#71908 this pr breaks modsuit icons before the first time they seal by
making the icon state be skin-standard-part
this fixes that by making them use base_icon_state instead of initial,
and also puts that in other places to reduce hardcoded stuff

## Why It's Good For The Game
le bug is le fix

## Changelog
🆑
fix: fixes modsuit icons
/🆑

code/modules/mod/mod_activation.dm

@@ -191,6 +191,7 @@
 ///Seals or unseals the given part
 /obj/item/mod/control/proc/seal_part(obj/item/clothing/part, seal)
 	if(seal)
+		part.icon_state = "[skin]-[part.base_icon_state]-sealed"
 		part.clothing_flags |= part.visor_flags
 		part.flags_inv |= part.visor_flags_inv
 		part.flags_cover |= part.visor_flags_cover
@@ -198,6 +199,7 @@
 		part.cold_protection = initial(part.cold_protection)
 		part.alternate_worn_layer = null
 	else
+		part.icon_state = "[skin]-[part.base_icon_state]"
 		part.flags_cover &= ~part.visor_flags_cover
 		part.flags_inv &= ~part.visor_flags_inv
 		part.clothing_flags &= ~part.visor_flags
@@ -205,17 +207,13 @@
 		part.cold_protection = NONE
 		part.alternate_worn_layer = mod_parts[part]
 	if(part == boots)
-		boots.icon_state = "[skin]-boots[seal ? "-sealed" : ""]"
 		wearer.update_worn_shoes()
 	if(part == gauntlets)
-		gauntlets.icon_state = "[skin]-gauntlets[seal ? "-sealed" : ""]"
 		wearer.update_worn_gloves()
 	if(part == chestplate)
-		chestplate.icon_state = "[skin]-chestplate[seal ? "-sealed" : ""]"
 		wearer.update_worn_oversuit()
 		wearer.update_worn_undersuit()
 	if(part == helmet)
-		helmet.icon_state = "[skin]-helmet[seal ? "-sealed" : ""]"
 		wearer.update_worn_head()
 		wearer.update_worn_mask()
 		wearer.update_worn_glasses()