Add SDK sandbox UIDs to network policy.

SDK sandbox processes run alongside app processes, and should follow
the same network policy as the app that they belong to. For the relevant
calls into the NetworkManager, add the corresponding SDK sandbox UID to
make sure they have the same policy.

Bug: 215012578
Test: atest NetworkPolicyManagerServiceTest
Change-Id: Iaa2283808071d285953a0de3ed018472a67a1510