Apply packages visibility to ContentResolver#getSyncAdapterTypes

Also, adds it to the test api for the Cts tests.

Bug: 153657222
Test: atest android.appenumeration.cts.AppEnumerationTests
Test: atest android.content.ContentResolverTest
Test: atest SyncAdapterSettingsHostSideTest
Change-Id: I9ac62a80c29351f05725c1636c52928b279840a0