message: [logging] Log RFC3339 timestamp for better granularity
  Currently, the timestamp in structured logs is just the day and time, in
  seconds.  This gives us better granularity by using a well known time
  format that will let us order all of the logs.
  Closes:
diff: @@ -8,7 +8,7 @@ use crate::{
  },
  LogLevel,
  };
  -use chrono::Utc;
  +use chrono::{SecondsFormat, Utc};
  use once_cell::sync::Lazy;
  use serde::Serialize;
  use serde_json::Value;
  @@ -95,15 +95,14 @@ pub struct StructuredLogEntry {
  impl StructuredLogEntry {
  pub fn new_unnamed() -> Self {
  let mut ret = Self::default();
  - ret.timestamp = Some(Utc::now().format("%F %T").to_string());
  + ret.timestamp = Some(Utc::now().to_rfc3339_opts(SecondsFormat::Millis, true));
  ret
  }
  pub fn new_named(category: &'static str, name: &'static str) -> Self {
  - let mut ret = Self::default();
  + let mut ret = Self::new_unnamed();
  ret.category = Some(category);
  ret.name = Some(name);
  - ret.timestamp = Some(Utc::now().format("%F %T").to_string());
  ret
  }
  