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/projectiles/guns/launcher/pneumatic.dm

@@ -30,7 +30,7 @@
 		return
 	. += "The valve is dialed to <b>[pressure_setting]%</b>."
 	if(tank)
-		. += "The tank dial reads <b>[tank.air_contents.return_pressure()] kPa</b>."
+		. += "The tank dial reads <b>[XGM_PRESSURE(tank.air_contents)] kPa</b>."
 	else
 		. += "Nothing is attached to the tank valve!"
 
@@ -101,9 +101,9 @@
 	if(T)
 		var/datum/gas_mixture/environment = T.return_air()
 		if(environment)
-			environment_pressure = environment.return_pressure()
+			environment_pressure = XGM_PRESSURE(environment)
 
-	fire_pressure = (tank.air_contents.return_pressure() - environment_pressure)*pressure_setting/100
+	fire_pressure = (XGM_PRESSURE(tank.air_contents) - environment_pressure)*pressure_setting/100
 	if(fire_pressure < 10)
 		to_chat(user, "There isn't enough gas in the tank to fire [src].")
 		return null