Disconnect BlockNotifyGenesisWait and RPCNotifyBlockChange properly. Remove no-op CClientUIInterface::[signal_name]_disconnect. (practicalswift)
Pull request description:
Resolves #15698. Changes: * Remove no-op `CClientUIInterface::[signal_name]_disconnect`. * Disconnect `BlockNotifyGenesisWait` and `RPCNotifyBlockChange` properly.
Backport of Core PR15699