DFB property changes. (#4590)

# About the pull request
part 2 out of 4 
This does a **big** touch up on defibrillation property in research

Well, to start off, max_level = 1 was removed. It appears warcrimes
forgot to remove it since process proc has benefits explicitly for
higher levels. I would call it a bug(oversight rather).

Second: Ghosts get notified when the chem starts to try and defib you,
so you dont just wonder how did you stand up, and pretty neat too.

Third: The >6 level of defib to apply healing like with actual item
defib is too high, so we move requirement down to >1 but make it heal
much, much worse at levels lower than 5.
eg it took 20 units to heal ~20 brute at level 3(you will literally
perma lmao), at level 5, however, this will go at around 2.5 per life
tick, level 8 will give 4 damage heal.
This is a balance change(buff) But hardly so since its research,
Research is already neglecting most of the time this property.

Fourth: removes one letter var, This whole file is entombed with them
but Im not doing that for now.

# Explain why it's good for the game


Defib property is way too underused and crudely made. This fixes it,
partially.

# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Put screenshots and videos here with an empty line between the
screenshots and the `<details>` tags.

</details>


# Changelog
:cl: kiVts
add: Ghosts get notified when they are being revived by DFB property
balance: DFB property healing threshold lowered, You can create DFB
property higher than one.
/:cl:

---------

Co-authored-by: Zonespace <[email protected]>

code/modules/reagents/chemistry_properties/prop_positive.dm

@@ -548,7 +548,7 @@
 	rarity = PROPERTY_RARE
 	category = PROPERTY_TYPE_REACTANT
 	value = 3
-	max_level = 1
+	COOLDOWN_DECLARE(ghost_notif)
 
 /datum/chem_property/positive/defibrillating/on_delete(mob/living/M)
 	..()
@@ -574,19 +574,33 @@
 /datum/chem_property/positive/defibrillating/process_dead(mob/living/M, potency = 1, delta_time)
 	if(!ishuman(M))
 		return
-	var/mob/living/carbon/human/H = M
-	H.apply_damage(-H.getOxyLoss(), OXY)
-	if(H.check_tod() && H.is_revivable() && H.health > HEALTH_THRESHOLD_DEAD)
-		to_chat(H, SPAN_NOTICE("You feel your heart struggling as you suddenly feel a spark, making it desperately try to continue pumping."))
-		playsound_client(H.client, 'sound/effects/Heart Beat Short.ogg', 35)
-		addtimer(CALLBACK(H, TYPE_PROC_REF(/mob/living/carbon/human, handle_revive)), 50, TIMER_UNIQUE)
-	else if (potency > POTENCY_MAX_TIER_1 && H.check_tod() && H.is_revivable() && H.health < HEALTH_THRESHOLD_DEAD) //Will heal if level is 7 or greater
-		to_chat(H, SPAN_NOTICE("You feel a faint spark in your chest."))
-		H.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, BRUTE)
-		H.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, BURN)
-		H.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, TOX)
-		H.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, CLONE)
-		H.apply_damage(-H.getOxyLoss(), OXY)
+	var/mob/living/carbon/human/dead = M
+	var/revivable = dead.check_tod() && dead.is_revivable()
+	if(revivable && (dead.health > HEALTH_THRESHOLD_DEAD))
+		addtimer(CALLBACK(dead, TYPE_PROC_REF(/mob/living/carbon/human, handle_revive)), 5 SECONDS)
+		to_chat(dead, SPAN_NOTICE("You feel your heart struggling as you suddenly feel a spark, making it desperately try to continue pumping."))
+		playsound_client(dead.client, 'sound/effects/heart_beat_short.ogg', 35)
+	else if ((potency >= 1) && revivable && dead.health <= HEALTH_THRESHOLD_DEAD) //heals on all level above 1. This is however, minimal.
+		to_chat(dead, SPAN_NOTICE("You feel a faint spark in your chest."))
+		dead.apply_damage(-potency * POTENCY_MULTIPLIER_VLOW, BRUTE)
+		dead.apply_damage(-potency * POTENCY_MULTIPLIER_VLOW, BURN)
+		dead.apply_damage(-potency * POTENCY_MULTIPLIER_VLOW, TOX)
+		dead.apply_damage(-potency * POTENCY_MULTIPLIER_VLOW, CLONE)
+		dead.apply_damage(-dead.getOxyLoss(), OXY)
+		if(potency > CREATE_MAX_TIER_1) //heal more if higher levels
+			dead.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, BRUTE)
+			dead.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, BURN)
+			dead.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, TOX)
+			dead.apply_damage(-potency * POTENCY_MULTIPLIER_LOW, CLONE)
+		if(dead.health < HEALTH_THRESHOLD_DEAD)
+			return
+		if(!COOLDOWN_FINISHED(src, ghost_notif))
+			return
+		var/mob/dead/observer/ghost = dead.get_ghost()
+		if(ghost?.client)
+			COOLDOWN_START(src, ghost_notif, 30 SECONDS)
+			playsound_client(ghost.client, 'sound/effects/adminhelp_new.ogg')
+			to_chat(ghost, SPAN_BOLDNOTICE("Your heart is struggling to pump! There is a chance you might get up!(Verbs -> Ghost -> Re-enter corpse, or <a href='?src=\ref[ghost];reentercorpse=1'>click here!</a>)"))
 	return TRUE
 
 /datum/chem_property/positive/hyperdensificating