Splits placeontop proc (#79702)

## About The Pull Request
I find the proc hard to read honestly. There's no reason we can't split
this into two functions - the secondary functionality is used only once,
in reader.dmm.
## Why It's Good For The Game
Code improvement
Glorious snake case
## Changelog
N/A nothing player facing

---------

Co-authored-by: san7890 <34697715+san7890@users.noreply.github.com>

code/modules/mapfluff/ruins/lavalandruin_code/puzzle.dm

@@ -173,7 +173,7 @@
 	//Setup random empty tile
 	empty_tile_id = pick_n_take(left_ids)
 	var/turf/empty_tile_turf = get_turf_for_id(empty_tile_id)
-	empty_tile_turf.PlaceOnTop(floor_type,null,CHANGETURF_INHERIT_AIR)
+	empty_tile_turf.place_on_top(floor_type, CHANGETURF_INHERIT_AIR)
 	var/mutable_appearance/MA = new(puzzle_pieces["[empty_tile_id]"])
 	MA.layer = empty_tile_turf.layer + 0.1
 	empty_tile_turf.add_overlay(MA)
@@ -182,7 +182,7 @@
 	var/list/empty_spots = left_ids.Copy()
 	for(var/spot_id in empty_spots)
 		var/turf/T = get_turf_for_id(spot_id)
-		T = T.PlaceOnTop(floor_type,null,CHANGETURF_INHERIT_AIR)
+		T = T.place_on_top(floor_type, CHANGETURF_INHERIT_AIR)
 		var/obj/structure/puzzle_element/E = new element_type(T)
 		elements += E
 		var/chosen_id = pick_n_take(left_ids)