Add reset and list for device config flags to SettingsProvider to

support command line debug tool.

Test: atest FrameworksCoreTests:SettingsProviderTest
      Further tested manually via command line (see ag/5613024)
Bug:109919982
Bug:113101834
Change-Id: Ib0d9e4c6d806ec3521ac49b8c05fbdad8b5b13d7