Address review comments at aosp/3249945

This change includes:
  1. Rename binder interfaces.
  2. Use a dedicated class to pass the result of
     get{Total|Iface|Uid}Stats, as it is 25% faster than passing
     a NetworkStats object through the binder interface.
  3. Remove the binder interface only used by the test.
  4. Remove NetworkStatsBinderTest on R and S, since the binder
     interface is removed, the mainlined service does not run on
     those versions and the chance of breaking these tests on
     R and S is low.
  5. Remove useless TODO comments.

Test: atest FrameworksNetTests:android.net.connectivity.com.android.server.net.NetworkStatsServiceTest \
      CtsNetTestCases:android.net.cts.NetworkStatsBinderTest \
      FrameworksNetIntegrationTests:com.android.server.net.integrationtests.NetworkStatsIntegrationTest
Bug: 372851500
Bug: 343260158

Change-Id: Ibd79a17218f54f0117d8ef5d7b9ec6073356f923
7 files changed