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.
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Backport of Core PR15699