Validate all INTERNET-providing VCN-managed networks

This change adds support for validating all VCN-underlying, INTERNET
exposing networks, including untrusted or restricted ones, given that
they are used for those purposes in other system components

Bug: 181281776
Test: FrameworksNetTests
Original-Change: https://android-review.googlesource.com/1705647
Merged-In: I16afa90d71cab60f1217d51a0332a2f778dd624c
Change-Id: I16afa90d71cab60f1217d51a0332a2f778dd624c