Add StatsD counters for media resolution results

[johnshaughnessy]

Adds telemetry to media resolution results.
This may be partially redundant with the more specific request types (for example:

        Statix.increment("ret.media_resolver.poly.requests")

and

        Statix.increment("ret.media_resolver.poly.ok")

), but still seems useful for monitoring server health.

Note: I don't know how to test this without simply deploying it because it looks like Statix is only configured for prod.