move the internal preview to canvas (#18930)

* move the internal preview to canvas

* use a helper

* basic readme prep

* .

* .

* transform  better

* byond can't handle icon states of large files...

* move fully to the rust version

* fix typing

* just wtf. NO

* fix the legacy path

* keep it all centralized

* tiny oversight

* unit test rewrite

* rename

* fix bad layering

* fixes a bunch of layering issues

* artifact

* move crash to log_runtime

* missing overlay warning

* why not

code/controllers/subsystems/plants.dm

@@ -38,7 +38,7 @@ SUBSYSTEM_DEF(plants)
 // Looks like shit but it's sort of necessary.
 /datum/controller/subsystem/plants/proc/setup()
 	// Build the icon lists.
-	for(var/icostate in cached_icon_states('icons/obj/hydroponics_growing.dmi'))
+	for(var/icostate in icon_states_fast('icons/obj/hydroponics_growing.dmi'))
 		var/split = findtext(icostate,"-")
 		if(!split)
 			// invalid icon_state
@@ -56,7 +56,7 @@ SUBSYSTEM_DEF(plants)
 			if(!(base in GLOB.forbidden_plant_growth_sprites))
 				accessible_plant_sprites[base] = ikey
 
-	for(var/icostate in cached_icon_states('icons/obj/hydroponics_products.dmi'))
+	for(var/icostate in icon_states_fast('icons/obj/hydroponics_products.dmi'))
 		var/split = findtext(icostate,"-")
 		var/base = copytext(icostate,1,split)
 		if(split)

code/controllers/subsystems/robot_sprites.dm

@@ -139,7 +139,7 @@ SUBSYSTEM_DEF(robot_sprites)
 		RS.icon_x = text2num(splitted[1])
 		RS.icon_y = text2num(splitted[2])
 		RS.vis_height = text2num(splitted[2])
-		var/list/icon_states = cached_icon_states(RS.sprite_icon)
+		var/list/icon_states = icon_states_fast(RS.sprite_icon)
 		for(var/icon in icon_states)
 			// testing whitelist functionality ckey-...
 			if(findtext(icon, regex("ckey-")))