Moves camera update handling to background subsystem, (maybe) fixing lag (#92208)

## About The Pull Request

When a camera update is triggered, it is instead added to a queue on a
background subsystem

An AI entering a camera chunk which is queued to update will force the
update immediately (bypassing the queue)

While the root problem of this is, ultimately, not addressed...

<img width="554" height="58"
alt="467828777-eff3f0e5-49d6-4997-b4d7-05eff6432155"
src="https://github.com/user-attachments/assets/c2d6a5f5-d958-463e-959f-116bd0dab475"
/>

...the change will ultimately prevent update spam from consuming all of
the server's resources - instead allocating updates to the backburner in
times of high server stress (or on multi-z maps)

## Changelog

🆑 Melbert
refactor: Refactored the way camera updates are handled to hopefully
reduce some lag. Report any oddities
/🆑

code/modules/admin/verbs/debug.dm

@@ -320,7 +320,7 @@ ADMIN_VERB(cmd_admin_areatest, R_DEBUG, "Test Areas", "Tests the areas for vario
 			areas_with_intercom.Add(A.type)
 		CHECK_TICK
 
-	for(var/obj/machinery/camera/C as anything in GLOB.cameranet.cameras)
+	for(var/obj/machinery/camera/C as anything in SScameras.cameras)
 		var/area/A = get_area(C)
 		if(!A)
 			dat += "Skipped over [C] in invalid location, [C.loc].<br>"