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/shieldgen/shield_capacitor.dm

@@ -123,7 +123,8 @@
 
 	if (PN)
 		var/power_draw = between(0, max_charge - stored_charge, charge_rate) //what we are trying to draw
-		power_draw = PN.draw_power(power_draw) //what we actually get
+		power_draw = POWERNET_POWER_DRAW(PN, power_draw) //what we actually get
+		DRAW_FROM_POWERNET(PN, power_draw)
 		stored_charge += power_draw
 
 	time_since_fail++

code/modules/shieldgen/shieldwallgen.dm

@@ -85,7 +85,8 @@
 		return FALSE
 
 	var/shieldload = between(500, max_stored_power - storedpower, (power_draw*seconds_per_tick))	//what we try to draw
-	shieldload = PN.draw_power(shieldload) //what we actually get
+	shieldload = POWERNET_POWER_DRAW(PN, shieldload) //what we actually get
+	DRAW_FROM_POWERNET(PN, shieldload)
 	storedpower += shieldload
 
 	//If we're still in the red, then there must not be enough available power to cover our load.