Fix mobile data usage didn't get increased for xlat464 traffic

Interface stats on stacked interfaces is usually clatd. For
xt_qtaguid supported device, the stats is already accounted
against its final egress interface by the kernel.
Framework side does not need to handle stats on statcked
interface at all.

However, on devices that support BPF offload, xlat464
packets are seen by the iptables rules as arriving on stack
interface only. Thus, add stack interface into accounting is
needed.

Bug: 136193260
Test: 1. atest FrameworksNetTests
      2. atest android.app.usage.cts.NetworkUsageStatsTest
      3. manual test on ipv6-only wifi network

Merged-In: I8ebbefbe4df00e40f4896a17fa52c8438d41286e
Change-Id: I8ebbefbe4df00e40f4896a17fa52c8438d41286e
(cherry-pick from aosp/1009306)