Add a DPM api to check if a pkg is restricted to use metered data.

We need this so that Settings can check if an app is
restricted by admin from using metered data.

Bug: 63700027
Test: manual
Test: atest com.android.server.devicepolicy.DevicePolicyManagerTest
Change-Id: I9a2ea9c458b0f10a3c3c6edcbe82da9eccaa51c3
7 files changed