[3.3.5] Combat/Threat rewrite - prep & refactor (#19966)

* Combat/Threat rewrite (PR #19930) prep work. Mostly refactors, and a compatibility layer on ThreatManager/HostileReference that allows scripts to be changed already.

(cherry picked from commit e2a1ccd118d129b96e09ff1a15ed0adb1d4a3897)

src/server/game/AI/ScriptedAI/ScriptedCreature.h

@@ -208,11 +208,16 @@ struct TC_GAME_API ScriptedAI : public CreatureAI
     //Plays a sound to all nearby players
     void DoPlaySoundToSet(WorldObject* source, uint32 soundId);
 
-    //Drops all threat to 0%. Does not remove players from the threat list
-    void DoResetThreat();
-
-    float DoGetThreat(Unit* unit);
-    void DoModifyThreatPercent(Unit* unit, int32 pct);
+    // Add specified amount of threat directly to victim (ignores redirection effects) - also puts victim in combat and engages them if necessary
+    void AddThreat(Unit* victim, float amount, Unit* who = nullptr);
+    // Adds/removes the specified percentage from the specified victim's threat (to who, or me if not specified)
+    void ModifyThreatByPercent(Unit* victim, int32 pct, Unit* who = nullptr);
+    // Resets the victim's threat level to who (or me if not specified) to zero
+    void ResetThreat(Unit* victim, Unit* who = nullptr);
+    // Resets the specified unit's threat list (me if not specified) - does not delete entries, just sets their threat to zero
+    void ResetThreatList(Unit* who = nullptr);
+    // Returns the threat level of victim towards who (or me if not specified)
+    float GetThreat(Unit const* victim, Unit const* who = nullptr);
 
     void DoTeleportTo(float x, float y, float z, uint32 time = 0);
     void DoTeleportTo(float const pos[4]);