Keep primitive members used by MessageUtils.

This includes in particular {Full,Network}Score.POLICY_* members
which were removed recently.

Before :
  Policies : 55&62&63
After :
  Policies : EVER_EVALUATED&EVER_VALIDATED&IS_VALIDATED

This patch also unifies the directives under Tethering/ for
simplicity.

Test: adb logcat & dumpsys connectivity & dumpsys tethering
Change-Id: I3d231fbaaebe233b2633da8bb880b5ad1613a32f