Cleanup more follower leaks (#20902)

* Cleanup more follower leaks

Rather than check stop everywhere we'll just check it on start and cleanup the old following. If someone were already following and followed something new the FollowedComponent would never get cleaned up and would never have its ref to the entity removed.

* Don't cause archetype changes

Content.Shared/Follower/FollowerSystem.cs

@@ -138,7 +138,20 @@ public void StartFollowingEntity(EntityUid follower, EntityUid entity)
             targetXform = Transform(targetXform.ParentUid);
         }
 
-        var followerComp = EnsureComp<FollowerComponent>(follower);
+        // Cleanup old following.
+        if (TryComp<FollowerComponent>(follower, out var followerComp))
+        {
+            // Already following you goob
+            if (followerComp.Following == entity)
+                return;
+
+            StopFollowingEntity(follower, followerComp.Following, deparent: false, removeComp: false);
+        }
+        else
+        {
+            followerComp = AddComp<FollowerComponent>(follower);
+        }
+
         followerComp.Following = entity;
 
         var followedComp = EnsureComp<FollowedComponent>(entity);
@@ -167,14 +180,14 @@ public void StartFollowingEntity(EntityUid follower, EntityUid entity)
 
         RaiseLocalEvent(follower, followerEv);
         RaiseLocalEvent(entity, entityEv);
-        Dirty(followedComp);
+        Dirty(entity, followedComp);
     }
 
     /// <summary>
     ///     Forces an entity to stop following another entity, if it is doing so.
     /// </summary>
     /// <param name="deparent">Should the entity deparent itself</param>
-    public void StopFollowingEntity(EntityUid uid, EntityUid target, FollowedComponent? followed = null, bool deparent = true)
+    public void StopFollowingEntity(EntityUid uid, EntityUid target, FollowedComponent? followed = null, bool deparent = true, bool removeComp = true)
     {
         if (!Resolve(target, ref followed, false))
             return;
@@ -186,8 +199,12 @@ public void StopFollowingEntity(EntityUid uid, EntityUid target, FollowedCompone
         if (followed.Following.Count == 0)
             RemComp<FollowedComponent>(target);
 
-        RemComp<FollowerComponent>(uid);
-        RemComp<OrbitVisualsComponent>(uid);
+        if (removeComp)
+        {
+            RemComp<FollowerComponent>(uid);
+            RemComp<OrbitVisualsComponent>(uid);
+        }
+
         var uidEv = new StoppedFollowingEntityEvent(target, uid);
         var targetEv = new EntityStoppedFollowingEvent(target, uid);