Use metered firewalls for metered uid policy

Since the underlying code in connectivity manager is moving to metered
firewalls to denote the uid policy for metered restrictions, NPMS can
start using them now.
Rather than having a single PENALTY_BOX, we have separate firewalls for
user and admin imposed restrictions. Once NPMS uses the appropriate
firewalls for these, it does not need to separately convey the blocked
reasons for metered restrictions on uids to the ConnectivityManager.

Flag: com.android.server.net.use_metered_firewall_chains

Test: atest FrameworksServicesTests:NetworkManagementServiceTest
Test: atest FrameworksServicesTests:NetworkPolicyManagerTest
Test: atest CtsHostsideNetworkPolicyTests

Bug: 336693007
Change-Id: I8da11ff663257d3dafcb5e22ae3313a9255ef0a6