Randpixel initialize (#20239)

Moved all calls of randpixel_xy in Initialize() (if they were in New())
Some tweaks of the proc

This should avoid some random CI failures due to it matching shifted
pixels as dirty vars

No player facing changes

code/game/objects/items.dm

@@ -1078,14 +1078,29 @@ modules/mob/living/carbon/human/life.dm if you die, you will be zoomed out.
 		return TRUE
 	return FALSE
 
-//Used for selecting a random pixel placement, usually on initialize. Checks for pixel_x/y to not interfere with mapped in items.
+/**
+ * Randomizes the pixel_x and pixel_y variables of the item if they are not already set, based on `randpixel`
+ *
+ * Returns `TRUE` if the item was randomized, `FALSE` otherwise
+ *
+ * This should _not_ be called from `New()`, only from `Initialize()` or other procs that are called after the maploader has already finished loading the item
+ */
 /obj/item/proc/randpixel_xy()
-	if(!pixel_x && !pixel_y)
-		pixel_x = rand(-randpixel, randpixel)
-		pixel_y = rand(-randpixel, randpixel)
-		return TRUE
-	else
+	SHOULD_NOT_SLEEP(TRUE)
+
+	#if defined(TESTING)
+	if(!(src.flags_1 & INITIALIZED_1))
+		stack_trace("Item [src] was not initialized before calling randpixel_xy()!")
 		return FALSE
+	#endif
+
+	// If the item is qdel'd, has already been randomized or has already a pixel_x or pixel_y set, don't do anything and return FALSE
+	if(QDELETED(src) || pixel_x || pixel_y)
+		return FALSE
+
+	pixel_x = rand(-randpixel, randpixel)
+	pixel_y = rand(-randpixel, randpixel)
+	return TRUE
 
 /obj/item/do_simple_ranged_interaction(var/mob/user)
 	if(user)

code/game/objects/items/stacks/tiles/tile_types.dm

@@ -26,8 +26,8 @@
 	item_flags = 0
 	obj_flags = 0
 
-/obj/item/stack/tile/New()
-	..()
+/obj/item/stack/tile/Initialize(mapload, amount)
+	. = ..()
 	randpixel_xy()
 
 /*