Research queue (#84731)

## About The Pull Request

<img alt="2dZbpr8MK1"
src="https://github.com/tgstation/tgstation/assets/3625094/dd78feba-224a-41a1-8d4a-83af3a8b68df">


Added an ability to queue up to one node per player in a techweb for an
automatic research.

You can queue up a node only when all requirements are met, but there
are not enough points.

People can't research when there is something in the queue, only add
things to the queue. So a 40 points node can't be researched if someone
queued up a 200 points node ahead of it.

When a node is enqueued by RD, it is placed in front of the queue.

The research button is available when the queue is empty.

TODO:

- [x] Bypass queue when the node cost is zero

## Why It's Good For The Game

No need to stay at the console to wait for the points. No "Research"
button spamming.

## Changelog

🆑
qol: Research nodes can be queued, one per player. RDs can place their
node at the beginning of the queue.
/🆑

code/modules/research/techweb/_techweb_node.dm

@@ -95,6 +95,17 @@
 
 	return actual_costs
 
+/datum/techweb_node/proc/is_free(datum/techweb/host)
+	var/list/costs = get_price(host)
+	var/total_points = 0
+
+	for(var/point_type in costs)
+		total_points += costs[point_type]
+
+	if(total_points == 0)
+		return TRUE
+	return FALSE
+
 /datum/techweb_node/proc/price_display(datum/techweb/TN)
 	return techweb_point_display_generic(get_price(TN))