replace magic numbers related to emp and explosion severity with defines (#26495)

replace even more magic emp and ex numbers

code/modules/power/engines/singularity/narsie.dm

@@ -84,7 +84,7 @@
 /obj/singularity/narsie/proc/godsmack(atom/A)
 	if(isobj(A))
 		var/obj/O = A
-		O.ex_act(1)
+		O.ex_act(EXPLODE_DEVASTATE)
 		if(O) qdel(O)
 
 	else if(isturf(A))

code/modules/power/gravitygenerator.dm

@@ -25,7 +25,7 @@ GLOBAL_LIST_EMPTY(gravity_generators)
 	flags_2 = NO_MALF_EFFECT_2
 
 /obj/machinery/gravity_generator/ex_act(severity)
-	if(severity == 1) // Very sturdy.
+	if(severity == EXPLODE_DEVASTATE) // Very sturdy.
 		set_broken()
 
 /obj/machinery/gravity_generator/blob_act(obj/structure/blob/B)