Use new BTC change address on RGB transfer

In this transaction we're sending the coin that's used to pay for the dust output and fees is sent back to the address:

https://mempool.space/testnet/tx/19e844a8a3d540438700f710bec6ad589bac8c0fea5266aeba7040fa7744ef5a

Notice that the address is reused. We should avoid address reuse, and instead, we should send the change to an unused BTC change wallet address.