Migrate the NETWORK_SCORER_APP to NETWORK_RECOMMENDATIONS_ENABLED.

If NETWORK_SCORER_APP has a non-null value then enabled
NETWORK_RECOMMENDATIONS_ENABLED.

Test: runtest --path frameworks/base/packages/SettingsProvider/test/src/com/android/providers/settings/SettingsProviderTest.java
BUG: 32913919
Change-Id: Ibea34f0a17539e9c583898dc336f807f92b33c54