ZoneLoading: Add ZoneMemory and the possibility to unload zones and their memory

src/ZoneCommon/Game/T6/GameT6.cpp

@@ -10,6 +10,14 @@ void GameT6::AddZone(Zone* zone)
     m_zones.push_back(zone);
 }
 
+void GameT6::RemoveZone(Zone* zone)
+{
+    const auto foundEntry = std::find(m_zones.begin(), m_zones.end(), zone);
+
+    if (foundEntry != m_zones.end())
+        m_zones.erase(foundEntry);
+}
+
 std::vector<Zone*> GameT6::GetZones()
 {
     return m_zones;