Implement accessibility telemtery in wear

As a part of this telemetry, log
 1. Accessiblity shortcut reported atom when stem primary button is
    triple pressed in wear
 2. log mistrigger occurred via System setting

Test: Tested logging of atom via : statsd_testdrive 266
Bug: 264540995
Test results:

On pressing triple press when its enabled, this was the output :

event_metrics {
  data {
    aggregated_atom_info {
      atom {
        accessibility_shortcut_reported {
          package_name: "com.google.android.marvin.talkback/com.google.android.marvin.talkback.TalkBackService"
          shortcut_type: A11Y_WEAR_TRIPLE_PRESS_GESTURE
          service_status: ENABLED
        }
      }
      elapsed_timestamp_nanos: 9304445032196
    }
  }
}
is_active: true

Change-Id: Ic348ed8762f2fac20c117671ee39a3acec8862bb