Add support for LoggingOnly changes

Throw an exception if someone tries to add an
override for a logging only change. Incorporate the restriction in the
OverrideValidator.

Test: change one change to be logging only, flash device, adb shell
dumpsys platform_compat
Test: atest com.android.server.compat.CompatConfigTest
Test: atest com.android.server.compat.OverrideValidatorImplTest
Bug: 148009004

Change-Id: I379c63f8b5c54500d9066be9363a186efd55d200