* Let alert rule service implement registry service
* Add count method to RuleStore interface
* Add implementation for deletion of alert rules
* Rename uid to folderUID in registry methods
* Check forceDeleteRule value for registry deletion
* Register alerting store with folder service
* Move folder test functions to separate package
* Add testing for alert rule counting, deletion
* Remove redundant count method
* Fix deleteChildrenInFolder signature
* Update pkg/services/ngalert/store/alert_rule.go
Co-authored-by: Sofia Papagiannaki <1632407+papagian@users.noreply.github.com>
* Add tests for nested folder deletion
* Refactor TestIntegrationNestedFolderService
* Add rules store as parameter for alertng provider
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Co-authored-by: Sofia Papagiannaki <1632407+papagian@users.noreply.github.com>