Move SystemConfig to services.jar

Migrates getDefaultVrComponents used by SettingsProvider and
adds a flag for hidden API enforcement to ApplicationInfo.

This removes any dependency on SystemConfig from core/ and
so it can be moved into services/core and exposed as a
mainline API.

This was done instead of exposing all of the methods through
SystemConfigManager, as that is designed for use across
processes, and it's more efficient to expose SystemConfig
directly for modules running in the server process.

Although VrManager is a nullable service, so getDefaultVrComponents
had to live there to simplify the logic and maintain the existing
behavior.

Bug: 236389629

Change-Id: I4c2b14e1d34aaf439ceb1a3f9c8207e5d39fa6c2