Add statsd atom for Legacy DRM usage

Example record:

  mediametrics_drmmanager_reported {
    timestamp_nanos: 1566518732000000000
    package_name: "android.drm.cts"
    package_version_code: 0
    media_apex_version: 0
    plugin_id: "libfwdlockengine"
    description: "OMA V1 Forward Lock"
    method: OPEN_CONVERT_SESSION
    mime_types: "application/vnd.oma.drm.message"
  }

Bug: 134789967
Test: statsd_testdrive
Change-Id: Id81722b7626db055a8333b15f9d7fdf4dd5c6dc9