True if the `secrethash` is for a lock with a known secret.

def is_secret_known(
        end_state: NettingChannelEndState,
        secrethash: SecretHash,
) -> bool:
    """True if the `secrethash` is for a lock with a known secret."""
    return (
        secrethash in end_state.secrethashes_to_unlockedlocks or
        secrethash in end_state.secrethashes_to_onchain_unlockedlocks
    )