Changes how disease biotypes are added (#45099)

* Makes inorganic biology and necrotic metabolism work immediately.

* Uhhh dont need that.

code/datums/diseases/advance/advance.dm

@@ -352,8 +352,7 @@
 	return id
 
 
-// Add a symptom, if it is over the limit (with a small chance to be able to go over)
-// we take a random symptom away and add the new one.
+// Add a symptom, if it is over the limit we take a random symptom away and add the new one.
 /datum/disease/advance/proc/AddSymptom(datum/symptom/S)
 
 	if(HasSymptom(S))
@@ -361,6 +360,7 @@
 
 	if(symptoms.len < (VIRUS_SYMPTOM_LIMIT - 1) + rand(-1, 1))
 		symptoms += S
+		S.OnAdd(src)
 	else
 		RemoveSymptom(pick(symptoms))
 		symptoms += S
@@ -368,12 +368,14 @@
 // Simply removes the symptom.
 /datum/disease/advance/proc/RemoveSymptom(datum/symptom/S)
 	symptoms -= S
+	S.OnRemove(src)
 
 // Neuter a symptom, so it will only affect stats
 /datum/disease/advance/proc/NeuterSymptom(datum/symptom/S)
 	if(!S.neutered)
 		S.neutered = TRUE
 		S.name += " (neutered)"
+		S.OnRemove(src)
 
 /*
 

code/datums/diseases/advance/symptoms/species.dm

@@ -8,12 +8,14 @@
 	level = 5
 	severity = 0
 
-/datum/symptom/undead_adaptation/Start(datum/disease/advance/A)
-	if(!..())
-		return
+/datum/symptom/undead_adaptation/OnAdd(datum/disease/advance/A)
 	A.process_dead = TRUE
 	A.infectable_biotypes |= MOB_UNDEAD
 
+/datum/symptom/undead_adaptation/OnRemove(datum/disease/advance/A)
+	A.process_dead = FALSE
+	A.infectable_biotypes -= MOB_UNDEAD
+
 /datum/symptom/inorganic_adaptation
 	name = "Inorganic Biology"
 	desc = "The virus can survive and replicate even in an inorganic environment, increasing its resistance and infection rate."
@@ -24,7 +26,9 @@
 	level = 5
 	severity = 0
 
-/datum/symptom/inorganic_adaptation/Start(datum/disease/advance/A)
-	if(!..())
-		return
+/datum/symptom/inorganic_adaptation/OnAdd(datum/disease/advance/A)
 	A.infectable_biotypes |= MOB_INORGANIC
+
+/datum/symptom/inorganic_adaptation/OnRemove(datum/disease/advance/A)
+	A.infectable_biotypes -= MOB_INORGANIC
+

code/datums/diseases/advance/symptoms/symptoms.dm

@@ -74,3 +74,9 @@
 
 /datum/symptom/proc/generate_threshold_desc()
 	return
+
+/datum/symptom/proc/OnAdd(datum/disease/advance/A)		//Overload when a symptom needs to be active before processing, like changing biotypes. 
+	return
+
+/datum/symptom/proc/OnRemove(datum/disease/advance/A)	//But dont forget to remove them too.
+	return