Lag War Day 4: Under Pressure, High Voltage (#21878)

Replace /datum/gas_mixture/proc/return_pressure with XGM_PRESSURE(xgm)
macro. Having such a relatively simple statement contributing proc
overhead to procs called millions of times is ridiculous

Rename /datum/gas_mixture/proc/zburn to react, deleting the old react
which was just an alias for it. Free proc overhead

Turn check_combustibility into a macro CHECK_COMBUSTIBLE(is_cmb, xgm).
also rewrite it slightly so that it only needs to do one pass. Its a bit
nasty so I apologize for that, but speeeeed.

Delete most powernet and obj/machinery/power procs for handling power,
replacing them with macros. The fact that we were unironically calling a
draw_power() on APCs to call draw_power() on their terminals to call
draw_power() on their powernet every single process tick was insane.

Turn `between` into a macro alias for clamp() since the param order is
different

turn `Percent` into a macro AS_PCT

Rewrite significant chunks of update_canmove so its not quite as
horrifying of a proc and hopefully doesn't eat the entire mob subsystem
every movement now

code/modules/power/singularity/emitter.dm

@@ -92,7 +92,7 @@
 
 /obj/machinery/power/emitter/update_icon()
 	ClearOverlays()
-	if(active && powernet && avail(active_power_usage))
+	if(active && powernet && POWER_AVAIL(src))
 		AddOverlays(emissive_appearance(icon, "[icon_state]_lights"))
 		AddOverlays("[icon_state]_lights")
 
@@ -149,7 +149,8 @@
 		update_icon()
 		return
 	if(((last_shot + fire_delay) <= world.time) && active)
-		var/actual_load = draw_power(active_power_usage)
+		var/actual_load = POWER_DRAW(src, active_power_usage)
+		DRAW_POWER(src, actual_load)
 		if(actual_load >= active_power_usage) //does the laser have enough power to shoot?
 			if(!powered)
 				powered = TRUE