Extend MetricsFactory so it can log to different LogWriters

- Renamed MetricsFractory to MetricsFeatureProvider, and access it using
  FeatureFactory.
- Instead of containing exactly 1 logWriter, MetricsFeatureProvider now
  contain a list.
- Added OnAttach event in Lifecycle. This is needed when a mixin
  requires Context to initialize itself.
- Updated tests.

Bug: 29575437
Test: make RunSettingsRoboTests
Change-Id: I7cc1528b9a744cd40088701e2bd115f41a8bf744

src/com/android/settings/overlay/FeatureFactory.java

@@ -21,6 +21,7 @@ import android.text.TextUtils;
 import android.util.Log;
 
 import com.android.settings.R;
+import com.android.settings.core.instrumentation.MetricsFeatureProvider;
 import com.android.settings.fuelgauge.PowerUsageFeatureProvider;
 
 /**
@@ -62,6 +63,8 @@ public abstract class FeatureFactory {
 
     public abstract SupportFeatureProvider getSupportFeatureProvider(Context context);
 
+    public abstract MetricsFeatureProvider getMetricsFeatureProvider();
+
     public abstract PowerUsageFeatureProvider getPowerUsageFeatureProvider();
 
     public static final class FactoryNotFoundException extends RuntimeException {