[BR02] Implement isUidNetworkingBlocked

This is needed for data stall detection mechanism in NetworkStack
to get the information about whether the network is blocked for
a given uid and conditions. Because the API will be called
frequently from NetworkStack to resolve all status for all uids
on the device, the API cannot call into the service which
creates IPC. Instead, the API need to directly access bpf maps
in the user process to retrieve the status. In this case the
user process is the network stack, the access control is provided
by linux file permission and selinux.

Test: atest FrameworksNetTests:android.net.connectivity.android.net.BpfNetMapsReaderTest
Test: atest FrameworksNetTests:android.net.connectivity.android.net.ConnectivityManagerTest
NO_IFTTT=Refactor only change for firewall chains definitions
Bug: 297836825

Change-Id: Iaf983b71ec98cbfe5152dcfade8a3120f938f135