clat bpf: add byte/packet counter

Bug: 285124667
Test: TreeHugger,
  atest FrameworksNetTests:android.net.connectivity.com.android.server.connectivity.ClatCoordinatorTest
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I5b59f0c05d41030f99160f68058c61eadd24fbbd
6 files changed