[NO GBP]Refactors how sheets are ejected from mat container (#77945)

## About The Pull Request
As #77936 pointed out an infinite while loop occurs in the recycler.
This was caused due to my recent mat changes as follows.

When the recycler eats up an item. If it found any material inside, it
would attempt to eject any sheets formed from it over here

https://github.com/tgstation/tgstation/blob/ed71735fb3d60e834abf5771525c98809a0bb6f5/code/game/machinery/recycler.dm#L199

Inside this proc i first create the sheets in `null space` why is
explained in the comment

https://github.com/tgstation/tgstation/blob/ed71735fb3d60e834abf5771525c98809a0bb6f5/code/datums/components/material/material_container.dm#L599-L600

After doing logging & stuff i then would move the sheets back into its
target turf so it could get merged again

https://github.com/tgstation/tgstation/blob/ed71735fb3d60e834abf5771525c98809a0bb6f5/code/datums/components/material/material_container.dm#L607-L608

Unfortunately this would trigger `COMSIG_ATOM_ENTERED` signal which the
recycler is hooked onto. The recycler would then eat the newly ejected
sheets again, which would cause more sheets to be ejected, which would
again trigger the signal `COMSIG_ATOM_ENTERED` and you have your
infinite loop.

I did this because i had no clue how to stop the stack from merging when
it got spawned and this was a poor solution, so upon examining the code
i found there is a var to specifically stops stacks from merging

https://github.com/tgstation/tgstation/blob/ed71735fb3d60e834abf5771525c98809a0bb6f5/code/game/objects/items/stacks/stack.dm#L81

Yup there is specific param called `merge=TRUE` which allows you to
explicitly stop stacks from merging. I now use this var and manually
merge stacks afterwards without calling `forceMove()` so it doesn't
trigger the recycler anymore which caused the infinite loops.

## Why It's good for the game
Writing checks to see if an object came from null space is weird. It
makes the code difficult to reason with as such situations never happen.
Now it makes sense for an atom to be moved "into" null space for e.g.
when it gets deleted but for an atom to "return back from it" never
happens and you shouldn't be bothered with figuring out how that
happened.

## Changelog
🆑
refactor: sheets are merged in a better way when ejected from machines &
material related stuff
/🆑

code/datums/components/material/material_container.dm

@@ -596,16 +596,26 @@
 	//eject sheets based on available amount after each iteration
 	var/count = 0
 	while(sheet_amt > 0)
-		//create sheets in null space so it doesn't merge & delete itself
-		var/obj/item/stack/sheet/new_sheets = new material.sheet_type(null, min(sheet_amt, MAX_STACK_SIZE), FALSE, list((material) = SHEET_MATERIAL_AMOUNT))
+		//don't merge yet. we need to do stuff with it first
+		var/obj/item/stack/sheet/new_sheets = new material.sheet_type(target, min(sheet_amt, MAX_STACK_SIZE), FALSE)
 		count += new_sheets.amount
 		//use material & deduct work needed
 		use_amount_mat(new_sheets.amount * SHEET_MATERIAL_AMOUNT, material)
 		sheet_amt -= new_sheets.amount
 		//send signal
 		SEND_SIGNAL(src, COMSIG_MATCONTAINER_SHEETS_RETRIEVED, new_sheets, context)
-		//now move to target so it gets merged
-		new_sheets.forceMove(target)
+		//no point merging anything into an already full stack
+		if(new_sheets.amount == new_sheets.max_amount)
+			continue
+		//now we can merge since we are done with it
+		for(var/obj/item/stack/item_stack in target)
+			if(item_stack == new_sheets || item_stack.type != material.sheet_type) //don't merge with self or different type
+				continue
+			//speed merge
+			var/merge_amount = min(item_stack.amount, new_sheets.max_amount - new_sheets.get_amount())
+			item_stack.use(merge_amount)
+			new_sheets.add(merge_amount)
+			break
 	return count
 
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