Ability to grant apps in app idle mode network.

This introduces a new whitelist that JobScheduler can use to request
that an app be whitelisted from network restrictions while in app idle.
This is intended to be a temporary whitelist and the app will still be
subject to other power saving restrictions.

Bug: 117846754
Bug: 111423978
Test: atest CtsHostsideNetworkTests
and atest NetworkPolicyManagerServiceTest
Change-Id: I75a77d95c0a2052b456cd011dcbc953fff09f34c