Make BatterySettings Asynchronous and use enhanced estimate

this CL changes BatteryInfo methods to all use the async style
callback approach it had for one of the methods. Non-async methods
are now annotated to only be used in worker threads. BatteryInfo
can now be obtained via callback by calling one of the async
methods. Alternatively if there is a worker thread available
the synchronous methods similar to the old ones can be used.

The callback methods have all been changed so that they cascade to a
async method that takes all the required info as paremeters. This
will minimize the amount of churn in files that currently use
BatteryInfo.

A new loader was created that can be used to get BatteryInfo in
places that wish to get it. This loader is used in
PowerUsageSummary to get the BatteryInfo.

Test: Robotests
Bug: 38399275
Bug: 38398949
Bug: 38399654
Change-Id: Ic5a82d8ca4c85fad1b883226327ec083badf861d

src/com/android/settings/fuelgauge/BatteryUtils.java

@@ -274,7 +274,7 @@ public class BatteryUtils {
 
     }
 
-    private long convertUsToMs(long timeUs) {
+    public long convertUsToMs(long timeUs) {
         return timeUs / 1000;
     }