Protecting new sealed state UTXO from disclosure during state transition

[dr-orlovsky]

As a part of the security model the UTXO's for all closed single-use seals for the past bound states must be known, i.e. all future owners of some state data will know UTXOs of past owners. However, such leak is not required for a state transfer process: a party transferring some state to the future owner may assign it to a UTXO commitment, which will be disclosed by the new owner to all future owners, but will keep UTXO hidden from the previous owner, increasing the security.

[dr-orlovsky]

I have implemented this in RGB code already; this also allows to hide UTXOs from unrelated transition graph branches