Add DeviceConfig.setProperties method for atomic writing.

This method accepts multiple flags and overrides the values of all flags
in the provided namespace atomically. If any listeners are registered
for that namespace it will also trigger a callback with all of the flags
that were changed (added, updated, or removed).

Test: atest FrameworksCoreTests:DeviceConfigTest
      atest FrameworksCoreTests:SettingsProviderTest
      atest SettingsProviderTest:DeviceConfigServiceTest
Bug: 136135417

Change-Id: I2e496a3807493750ba8891dd6390055c919b5f45