Ensure bitcoin ops always include a change address

[obycode]

The Bitcoin transactions generated by the Stacks miner must always have a change address. If there is no change address, then the op is treated as invalid. In testnet/stacks-node/src/burnchains/bitcoin_regtest_controller.rs, we need to ensure that this is the case.

Background: naka-1 stalled after a restart and it was discovered that the VRF key register was invalid because it had no change address while the node expected 2 outputs: the OP_RETURN and the change.

[ASuciuX]

Should this be closed as the PR got merged?

[blockstack-devops]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.