adds snake coiling (#15514)

* new signals for resting and stop pulling

these are to be used as signals that will cancel the coiling

* Create coiling.dm

* Update coiling.dm

* adds sprite accessory for coiled naga

* main changes that apply the actual visuals to the coiling mechanics

* adds message to coiling, fixes offset, adds action icon

* coil offset was using old direction

* reordering

* fixes coil sprite not disappearing

* fixes offsets, solves loadout issue

* follows lin's suggestion and adds support for slimes by making it entirely handled in handle mutant

code/modules/mob/dead/new_player/sprite_accessories/_sprite_accessories.dm

@@ -28,10 +28,9 @@
 	for(var/path in typesof(prototype))
 		if(path == prototype && skip_prototype)
 			continue
-		if(roundstart)
-			var/datum/sprite_accessory/P = path
-			if(initial(P.locked))
-				continue
+		var/datum/sprite_accessory/P = path
+		if((roundstart && initial(P.locked)) || initial(P.ignore))
+			continue
 		var/datum/sprite_accessory/D = new path()
 
 		if(D.icon_state)
@@ -64,6 +63,7 @@
 	var/mutant_part_string //Also used in species.handle_mutant_bodyparts() to generate the overlay icon state.
 	var/alpha_mask_state
 	var/matrixed_sections = MATRIX_NONE //if color_src is MATRIXED, how many sections does it have? 1-3
+	var/ignore = FALSE //NEVER include in customization if set to TRUE
 
 	//Special / holdover traits for Citadel specific sprites.
 	var/extra = FALSE

code/modules/mob/dead/new_player/sprite_accessories/legs_and_taurs.dm

@@ -126,6 +126,11 @@
 	hide_legs = USE_SNEK_CLIP_MASK
 	matrixed_sections = MATRIX_RED_GREEN
 
+/datum/sprite_accessory/taur/naga/coiled
+	name = "Naga (coiled)"
+	icon_state = "naga_coiled"
+	ignore = TRUE
+
 /datum/sprite_accessory/taur/otie
 	name = "Otie"
 	icon_state = "otie"