* introduce a new action "alert.provisioning.secrets:read" and role "fixed:alerting.provisioning.secrets:reader"
* update alerting API authorization layer to let the user read provisioning with the new action
* let new action use decrypt flag
* add action and role to docs
* 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
