Add property contexts for vts props

vts_config_prop and vts_status_prop are added to remove exported*_prop.
ro.vts.coverage becomes vts_config_prop, and vts.native_server.on
becomes vts_status_prop.

Bug: 155844385
Test: Run some vts and then getprop, e.g. atest \
      VtsHalAudioEffectV4_0TargetTest && adb shell getprop
Test: ro.vts.coverage is read without denials
Change-Id: Ic3532ef0ae7083db8d619d80e2b73249f87981ce
8 files changed