Fix network usage stats on 464xlat tethered.

Usage stats corrections for 464xlat in NetworkStatsFactory are not applied
to tethered traffic. Add adjustments in NetworkStatsService. After
migrating external callers off NetworkStatsFactory, we will be able to
only apply adjustments in NetworkStatsService and remove stacked
interface tracking from NetworkStatsFactory.
Bug: 72107146
Fixes: 72107146
Test: runtest frameworks-net & manual - checked corrected network usage
Merged-In: Ieb25c41c651499fdd01225ae5ac21d95e3d823f5
Merged-In: I016722f3a0ae2ae0a1d48bfacc4fe07ee3578ef7
(cherry-pick of aosp I5ce450e616b4fddf21f2a491fe5d0c9e9f969bda)

Change-Id: Id41cf22a0f9a63cb1832e9375bfb045861f08e52