Migrate the NETWORK_SCORER_APP Setting.

Migrate the value of NETWORK_SCORER_APP to the USE_OPEN_WIFI_PACKAGE
Setting if the following conditions are true:
  * NETWORK_SCORER_APP has a value
  * An active scorer/recommender is present.
  * The active scorer specifies a valid UseOpenWifiActivity.
  * The NETWORK_SCORER_APP value matches the package name of the
    UseOpenWifiActivity or the active scorer.

Test: runtest frameworks-services -c com.android.server.NetworkScorerAppManagerTest
Bug: 36718516
Change-Id: I7d7a56c62b4a7f4a0e43824fbb2075e80d7a753b