feat: log event queue length at log level "trace" — radicle-ci-broker

This reduces log spam.

Signed-off-by: Lars Wirzenius liw@liw.fi

 use std::{path::Path, sync::Mutex, time::Duration};
 use radicle::{git::raw::Oid, identity::RepoId, node::Event};
 use slog::{debug, error, info, o, warn, Drain};
 use slog::{debug, error, info, o, trace, warn, Drain};
 use slog_scope::GlobalLoggerGuard;
 use crate::{

     );
 }
 pub fn queueproc_queue_length(len: usize) {
     trace!(
         slog_scope::logger(),
         "event queue length"; "length" => len);
 }
 pub fn queueproc_picked_event(id: &QueueId, event: &QueuedCiEvent) {
     info!(
         slog_scope::logger(),

     fn pick_event(&self) -> Result<Option<QueuedCiEvent>, QueueError> {
         let ids = self.db.queued_ci_events().map_err(QueueError::db)?;
         logger::debug2(format!("queue in db has {} events", ids.len()));
         logger::queueproc_queue_length(ids.len());
         let mut queue = vec![];
         for id in ids.iter() {