Add eventlogging::service::reporter for reporting to StatsD

* Adds an eventlogging::service resource for eventlogging-reporter instances,
  added to EventLogging in I4cc35bd8e.
* Provision such an instance on vanadium, reporting to statsd.eqiad.wmnet.

Change-Id: I595f2c15d92426dfc072452a1f1627c0d5cebe0a