Consolidate all wrappers used for testing.

- Add the wrapper package and move all wrappers to the wrapper package.
- Get rid of some wrapper interface/impl implementation and have a
wrapper class directly.

Bug: 65634579
Test: make RunSettingsRoboTests
Change-Id: Ic757d8f7bacfa7a034c7e692205bc1dc4b0e1de1

tests/robotests/src/com/android/settings/display/BrightnessLevelPreferenceControllerTest.java

@@ -32,6 +32,7 @@ import android.support.v7.preference.PreferenceScreen;
 
 import com.android.settings.testutils.SettingsRobolectricTestRunner;
 import com.android.settings.TestConfig;
+import com.android.settings.wrapper.PowerManagerWrapper;
 
 import org.junit.Before;
 import org.junit.Test;