Fix prediction/interpolation interaction with authority transfer

[cBournhonesque]

Fixes #639

Prediction/Interpolation was not working correctly when combined with authority transfer.
An example use case is:

• spawn E1 on client C1
• transfer authority to server S, with prediction/interpolation enabled

How do we make sure that C1 will now spawn a predicted/interpolated entity?

This PR accomplishes this with several changes:

• when the authority is transferred, the new authoritative peer (for example server S) will check if the old authority wants to have prediction/interpolation. If it's the case, we:
  • pass that information directly in the AuthorityChange message. (we cannot send a separate ShouldBePredicted component insert, because that message might arrive before the AuthorityChange message so it will be discarded by C1)
  • send a Spawn message, so that C1 has a receiver GroupChannel and can update the ConfirmedTick (needed for prediction/interpolation). (Another option would be to not have a Spawn message at all but to include the ReplicationGroup in the AuthorityChange message so that upon receipt C1 can create a GroupChannel.) We make sure that on the receiver side, if we receive a Spawn for an existing entity we still update the local_entity_to_group for the receiver channel
  • update the sender GroupChannel on S to have an updated send_tick so that we don't send redundant component updates to C1, we only send updates since the authority transfer started. (Fixes Think about how to replicate changes after authority-transfer #758)

This PR adds one important restriction:

• if you transfer authority to a peer P, the peer P MUST have added the Replicate bundle before the authority transfer is done