* Create API test for overwriting invalid alertmanager config
* Avoid requiring alertmanager readiness for config changes
* AlertmanagerSrv depends on functionality rather than concrete types
* Add test for non-ready alertmanagers
* Additional cleanup and polish
* Back out previous integration test changes
* Refactor of tests incorrectly caused a test to become redundant
* Use pre-existing fake secret service
* Drop unused interface
* Test against concrete MultiOrgAlertmanager re-using fake infra from other tests
* Fix linter error
* Empty commit to rerun checks
* Alerting: Persist notification log and silences to the database
This removes the dependency of having persistent disk to run grafana alerting. Instead of regularly flushing the notification log and silences to disk we now flush the binary content of those files to the database encoded as a base64 string.
