astron.libpython: Implement packing of `required` fields @ `send_STATESERVER_CREATE_OBJECT_WITH_REQUIRED`

[maxrdz]

When an astron.libpython AI repository sends the STATESERVER_CREATE_OBJECT_WITH_REQUIRED it doesn't even pack the required fields because its missing this implementation. Need this to be fixed to add back the required keyword to the set_xyzh field in DistributedAvatar in the DC file.