Alerting: Fix provenance guard checks for Alertmanager configuration to not cause panic when compared nested objects (#69009)
* fix current settings parsed as new
* replace map comparison with cmp.Diff and log the diff
(cherry picked from commit e00260465b)
Co-authored-by: Yuri Tseretyan <yuriy.tseretyan@grafana.com>
* introduce alias for json.RawMessage with name RawMessage. This is needed to keep raw JSON and implement a marshaler for YAML, which does not seem to be used but there are tests that fail.
* replace usage of simplejson with RawMessage in NotificationChannelConfig
* remove usage of simplejson in tests
* change migration code to convert simplejson to raw message