Address Puller API Feedback

1. Rename registerPullAtomCallback to setPullAtomCallback
2. Rename unregisterPullAtomCallback to clearPullAtomCallback
3. Add getters to PullAtomMetadata
4. Change Ns to Millis (when I tried to make it Nanos, I received a
built time error saying to prefer millis unless we need the precision.
We do not need the precision, so I changed it).
5. Fix out of order params.

I did not change usePooledBuffer to setPooledBuffer because I think use
is more appropriate for our use case.

Test: make
Test: atest PullAtomMetadataTest
Test: atest GtsStatsdHostTestCases
Bug: 149475498

Change-Id: Ib07aa57a6e02c77917fe0e65a3d4a77c00ce8565

location/java/com/android/internal/location/gnssmetrics/GnssMetrics.java

@@ -624,7 +624,7 @@ public class GnssMetrics {
 
     private void registerGnssStats() {
         mPullAtomCallback = new StatsPullAtomCallbackImpl();
-        mStatsManager.registerPullAtomCallback(
+        mStatsManager.setPullAtomCallback(
                 FrameworkStatsLog.GNSS_STATS,
                 null, // use default PullAtomMetadata values
                 BackgroundThread.getExecutor(), mPullAtomCallback);