Core/Movement: Replace old TargetedMovementGenerator into ChaseMovementGenerator and FollowMovementGenerator, full rewrite for both.

Port From (https://github.com/TrinityCore/TrinityCore/commit/14939204955d1a24fe465cdfcbf307daf3ce4f09)

Source/Game/Entities/Unit/Unit.cs

@@ -44,7 +44,6 @@ namespace Game.Entities
             m_combatManager = new CombatManager(this);
             m_threatManager = new ThreatManager(this);
             _spellHistory = new SpellHistory(this);
-            m_FollowingRefManager = new RefManager<Unit, ITargetedMovementGeneratorBase>();
 
             ObjectTypeId = TypeId.Unit;
             ObjectTypeMask |= TypeMask.Unit;
@@ -454,6 +453,8 @@ namespace Game.Entities
 
                 RemoveAreaAurasDueToLeaveWorld();
 
+                RemoveAllFollowers();
+
                 if (!GetCharmerGUID().IsEmpty())
                 {
                     Log.outFatal(LogFilter.Unit, "Unit {0} has charmer guid when removed from world", GetEntry());
@@ -1312,6 +1313,13 @@ namespace Game.Entities
 
         public Totem ToTotem() { return IsTotem() ? (this as Totem) : null; }
         public TempSummon ToTempSummon() { return IsSummon() ? (this as TempSummon) : null; }
+
+        void RemoveAllFollowers()
+        {
+            while (!m_followingMe.Empty())
+                m_followingMe[0].SetTarget(null);
+        }
+
         public virtual void SetDeathState(DeathState s)
         {
             // Death state needs to be updated before RemoveAllAurasOnDeath() is called, to prevent entering combat
@@ -1563,11 +1571,8 @@ namespace Game.Entities
 
         public bool IsCharmedOwnedByPlayerOrPlayer() { return GetCharmerOrOwnerOrOwnGUID().IsPlayer(); }
 
-        public void AddFollower(FollowerReference pRef)
-        {
-            m_FollowingRefManager.InsertFirst(pRef);
-        }
-        public void RemoveFollower(FollowerReference pRef) { } //nothing to do yet
+        public void FollowerAdded(AbstractFollower f) { m_followingMe.Add(f); }
+        public void FollowerRemoved(AbstractFollower f) { m_followingMe.Remove(f); }
 
         public uint GetCreatureTypeMask()
         {