Function supervise_undeliverable_messages_with

pub fn supervise_undeliverable_messages_with<R, F>(
    rx: PortReceiver<Undeliverable<MessageEnvelope>>,
    resolve_sink: R,
    on_undeliverable: F,
)
where
    R: FnMut() -> Option<PortHandle<ActorSupervisionEvent>> + Send + 'static,
    F: Fn(&MessageEnvelope) + Send + Sync + 'static,

Drain undeliverables and convert them into ActorSupervisionEvent, using a caller-provided resolver to obtain the (possibly late) sink. If the resolver returns None, we log and drop the undeliverable.