SearchFeatureProvider's context field is removed

SearchFeatureProvider was holding on to a context and
outlived the SettingsActivity, thus leaking the activity.
The context was passed into most methods, and thus it
makes more sense to pass it in to every method.

Bug: 33677967
Test: Run MakeSettingsRoboTests
Change-Id: Ia82f30e7e0b83587b4baeef28e81da6b8e4303fe

tests/robotests/src/com/android/settings/dashboard/DashboardFeatureProviderImplTest.java

@@ -124,7 +124,7 @@ public class DashboardFeatureProviderImplTest {
         tile.intent = new Intent();
         tile.intent.setComponent(new ComponentName("pkg", "class"));
 
-        when(mActivity.getApplicationContext().getSystemService(Context.USER_SERVICE))
+        when(mActivity.getSystemService(Context.USER_SERVICE))
                 .thenReturn(mUserManager);
 
         mImpl.bindPreferenceToTile(mActivity, preference, tile, "123", Preference.DEFAULT_ORDER);