2ffa45267f
When XT stats are available, transition to prefer them over DEV, since they aren't subject to hardware driver bugs. Only switches at the first atomic XT bucket, and adds a Settings.Secure flag to force back to DEV if needed. Includes tests to cover transition. Fix tests where device overlay would change which network types reflected data usage. Test both history and summary APIs. Fixed collection timestamps to reflect full buckets. Bug: 6504744 Change-Id: Idd7f3b2fdb064c36547c85c51c214fd938c59b7e