fix(Core/Movement): add creature formation movement generator (#25030)

Co-authored-by: Shauren <shauren.trinity@gmail.com>
Co-authored-by: Rocco Silipo <108557877+Rorschach91@users.noreply.github.com>

src/server/game/Movement/AbstractFollower.cpp

@@ -0,0 +1,28 @@
+/*
+ * This file is part of the AzerothCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "AbstractFollower.h"
+#include "Unit.h"
+
+void AbstractFollower::SetTarget(Unit* unit)
+{
+    if (unit == GetTarget())
+        return;
+
+    i_target.link(unit, this);
+    _target = i_target.getTarget();
+}