Macro tor_hsservice::status::impl_status_sender

macro_rules! impl_status_sender {
    ($sender:ident, $field:ident) => { ... };
}

A helper for implementing PublisherStatusSender and IptMgrStatusSender.

TODO: this macro is a bit repetitive, it would be nice if we could reduce duplication even further (and auto-generate a note_<state> function for every State variant).