Enforce the calling permissions within NetworkRecommendationProvider.

Had to add a new ctor to get a Context instance and deprecate the
single arg ctor. Since this was being done I also took the opportunity
to replace the Handler param with an Executor which is more
appropriate in this case.

I'll remove the deprecated ctor once I've updated all of its
call points.

Test: adb shell am instrument -e class android.net.NetworkRecommendationProviderTest -w com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Bug: 34518584
Change-Id: Ic2441655d69838ae9caa7d598e876dec36e15363