[MIRROR] MODLink System (+ NWTLMM) [MDB IGNORE] (#23199)

* MODLink System (+ NWTLMM) (#77639)

## About The Pull Request
A pact made with `@ Kapu1178`
Small changes you should not care about:
RD MODsuit outfit (admin only) no longer has a beret that blocks the
activation of the suit
The beret used by death squad officers no longer is blocked from being
put on a hat stabilizer module
Admins can now Shear matrices of objects in Modify Transform
Multitool buffers have been a little refactored to use a setter proc
that saves them from causing hard dels
Cooler stuff:
A revival and remake of [Nobody Wants To Learn Matrix
Math](https://github.com/tgstation/tgstation/pull/59103), this time with
additional tooling for quick matrix calculations.

![image](https://github.com/tgstation/tgstation/assets/23585223/eb387738-0839-463a-aed8-4703d139b11a)
The MODLink system, available through every MODsuit and MODLink scryers
(a neck item obtainable from advanced modsuit research or
charliestation)
Let's you make a holographic call with any other MODLink user, where you
can chat in realtime and see what's up with em

![image](https://github.com/tgstation/tgstation/assets/23585223/5a822f9f-e823-497e-b766-40055f2fc0d6)
![image](https://github.com/tgstation/tgstation/assets/23585223/062983ee-6058-4e78-a3aa-bccda1a3e224)

## Why It's Good For The Game
Adds a fun way for the crew to communicate with each other that can be
done in real-time with relative privacy compared to radio.

## Changelog
🆑 Fikou, Armhulen, Sheets (+rep for Mothblocks and Potato)
fix: RD MODsuit outfit (admin only) no longer has a beret that blocks
the activation of the suit
fix: The beret used by death squad officers no longer is blocked from
being put on a hat stabilizer module
admin: Admins can now Shear matrices of objects in Modify Transform
admin: Admins now have access to Test Matrices in the VV dropdown, an
all-in-one tool for editing transforms.
add: MODLink system, available through scryers (from RnD and Charlie
Station) and through MODsuits. Lets you call people with holographs!
/🆑

* MODLink System (+ NWTLMM)

---------

Co-authored-by: Fikou <23585223+Fikou@users.noreply.github.com>

code/game/objects/items/devices/multitool.dm

@@ -30,7 +30,7 @@
 	custom_premium_price = PAYCHECK_COMMAND * 3
 	toolspeed = 1
 	usesound = 'sound/weapons/empty.ogg'
-	var/obj/machinery/buffer // simple machine buffer for device linkage
+	var/datum/buffer // simple machine buffer for device linkage
 	var/mode = 0
 
 /obj/item/multitool/examine(mob/user)
@@ -41,6 +41,17 @@
 	user.visible_message(span_suicide("[user] puts the [src] to [user.p_their()] chest. It looks like [user.p_theyre()] trying to pulse [user.p_their()] heart off!"))
 	return OXYLOSS//theres a reason it wasn't recommended by doctors
 
+/obj/item/multitool/proc/set_buffer(datum/buffer)
+	if(buffer)
+		UnregisterSignal(buffer, COMSIG_QDELETING)
+	if(QDELETED(buffer))
+		return
+	src.buffer = buffer
+	RegisterSignal(buffer, COMSIG_QDELETING, PROC_REF(on_buffer_del))
+
+/obj/item/multitool/proc/on_buffer_del(datum/source)
+	SIGNAL_HANDLER
+	buffer = null
 
 // Syndicate device disguised as a multitool; it will turn red when an AI camera is nearby.