Function init 

pub(crate) fn init<TContext: Spawner>(
    context: TContext,
    marshal: Mailbox<Scheme<PublicKey, MinSig>, Standard<Block>>,
    epocher: FixedEpocher,
    execution_node: TempoFullNode,
    state: FeedStateHandle,
) -> (Actor<TContext>, Mailbox)

Initialize the feed actor and mailbox.