Modify fire_act to temperature_expose where needed

This commit changes a bunch of objects fire_act's to temperature_expose,
to allow for superhot gas to act like an actual hotspot. This behaviour is
consistant with -tg-.

code/modules/events/spacevine.dm

@@ -7,3 +7,4 @@
 	else
 		biomass_infestation()
 	spacevines_spawned = 1
+v

code/modules/mob/living/carbon/alien/special/facehugger.dm

@@ -65,7 +65,7 @@ var/const/MAX_ACTIVE_TIME = 400
 		Die()
 	return
 
-/obj/item/clothing/mask/facehugger/fire_act(datum/gas_mixture/air, exposed_temperature, exposed_volume)
+/obj/item/clothing/mask/facehugger/temperature_expose(datum/gas_mixture/air, exposed_temperature, exposed_volume)
 	if(exposed_temperature > 300)
 		Die()
 	return

code/modules/power/lighting.dm

@@ -579,7 +579,7 @@
 
 // called when on fire
 
-/obj/machinery/light/fire_act(datum/gas_mixture/air, exposed_temperature, exposed_volume)
+/obj/machinery/light/temperature_expose(datum/gas_mixture/air, exposed_temperature, exposed_volume)
 	if(prob(max(0, exposed_temperature - 673)))   //0% at <400C, 100% at >500C
 		broken()