Alerting: Allow administrators delete rules permanently via UI (#101974)

* add query parameter to existing APIs to control the permanent deletion of rules
* add GUID to gettable rule
* add new endpoint /ruler/grafana/api/v1/trash/rule/guid/{RuleGUID} to delete rules from trash permanently

---------

Signed-off-by: Yuri Tseretyan <yuriy.tseretyan@grafana.com>

pkg/services/ngalert/api/authorization.go

@@ -65,6 +65,8 @@ func (api *API) authorize(method, path string) web.Handler {
 				ac.EvalPermission(ac.ActionAlertingRuleDelete, scope),
 			),
 		)
+	case http.MethodDelete + "/api/ruler/grafana/api/v1/trash/rule/guid/{RuleGUID}":
+		return middleware.ReqOrgAdmin
 
 	// Grafana rule state history paths
 	case http.MethodGet + "/api/v1/rules/history":