Sync PRIV_APP_OOB_ENABLED setting to pm.dexopt.priv-apps-oob

The settings value is used as a proxy for server side experiment to
populate configuration to the device.  This is only for experiment and
should be removed later.

Test: adb shell settings put global priv_app_oob_enabled 0
      # saw pm.dexopt.priv-apps-oob changed to false
Test: adb shell settings put global priv_app_oob_enabled 1
      # saw pm.dexopt.priv-apps-oob changed to true
Bug: 67415855
Bug: 63920015

Change-Id: I4eb2beb14cd2c86c4bfc439d9742e95d3aba45a9