NetworkStack: Allow modules with network_stack uid

The wifi service will start running with network_stack uid, so allow
modules with the same uid to use the network stack interfaces.

Note: Only modules signed with the same certificate (same as network_stack
APK) can share the uid, so this is restricted to Google signed modules.

Bug: 113174748
Test: Local wifi stack testing
Change-Id: I0fa1eef691601afd837a83a0dd041f8870ddfc77
(cherry-picked from 204d6c5b211c7ad5cb71b885bcb1bf4fa1a34c21)