cleanup _HELPERS/_lists.dm and all the necessary files (#61827)

Bring _HELPERS/_lists.dm to latest standards by:
-Adding proper documentation and fixing existing one
-Giving vars proper names
-Procs now use snake case as per standard (many files that use those procs will be affected)

code/modules/admin/view_variables/modify_variables.dm

@@ -142,7 +142,7 @@ GLOBAL_PROTECT(VVpixelmovement)
 
 		if(variable == "(CLEAR NULLS)")
 			L = L.Copy()
-			listclearnulls(L)
+			list_clear_nulls(L)
 			if (!O.vv_edit_var(objectvar, L))
 				to_chat(src, "Your edit was rejected by the object.", confidential = TRUE)
 				return
@@ -152,7 +152,7 @@ GLOBAL_PROTECT(VVpixelmovement)
 			return
 
 		if(variable == "(CLEAR DUPES)")
-			L = uniqueList(L)
+			L = unique_list(L)
 			if (!O.vv_edit_var(objectvar, L))
 				to_chat(src, "Your edit was rejected by the object.", confidential = TRUE)
 				return
@@ -306,7 +306,7 @@ GLOBAL_PROTECT(VVpixelmovement)
 		for (var/V in O.vars)
 			names += V
 
-		names = sortList(names)
+		names = sort_list(names)
 
 		variable = input("Which var?","Var") as null|anything in names
 		if(!variable)