Xenomorphs fixes and improvements (#3548)

This pr makes xenomorphs less awful via some additions and porting some fixes:
-removes the NO_MINOR_CUT that is not used anywhere and replace with NO_EMBED that stops things from embedding into mobs, like xenomorphs, shadow people and golems
-adds the night vision verbs to xenomorphs
-fixes aliens eggs layers behind under their weeds
-fixes some hud things missing
-makes their limbs unbreakable

This should make them a bit less buggy.

code/modules/organs/organ_external.dm

@@ -996,6 +996,8 @@ Note that amputating the affected organ does in fact remove the infection from t
 /obj/item/organ/external/proc/embed(var/obj/item/weapon/W, var/silent = 0, var/supplied_message)
 	if(!owner || loc != owner)
 		return
+	if(species.flags & NO_EMBED)
+		return
 	if(!silent)
 		if(supplied_message)
 			owner.visible_message("<span class='danger'>[supplied_message]</span>")