Updates to Settings.Config and SettingsProvider for the DeviceConfig API surface.

Remove tags from Settings.Config, as we don't need them for anything yet. Add resetMode and prefix args to the reset call. Remove references to user IDs for config table methods. Force settings state to stop treating all values set by system packages as the new default value, for the config table only.

Test: atest SettingsProviderTest:DeviceConfigServiceTest
      atest FrameworksCoreTests:SettingsProviderTest
Bug:109919982
Change-Id: Ia80c65ac6c0a91ab2b36742e6d446918acbb2f45