fix(Scripts/BlackwingLair): Razorgore improvements (#10971)

- Rewrite reset events
- Use proper healing spell on phase transition
- Now uses abilities during phase 1
- Phase transition scripted - mobs now run away

src/server/game/Entities/Creature/Creature.cpp

@@ -3524,3 +3524,8 @@ void Creature::SetRespawnTime(uint32 respawn)
 {
     m_respawnTime = respawn ? GameTime::GetGameTime().count() + respawn : 0;
 }
+
+void Creature::SetCorpseRemoveTime(uint32 delay)
+{
+    m_corpseRemoveTime = GameTime::GetGameTime().count() + delay;
+}