AlertingNG: Split into several packages (#31719)

* AlertingNG: Split into several packages

* Move AlertQuery to models

pkg/services/ngalert/api/instance_api.go

@@ -0,0 +1,19 @@
+package api
+
+import (
+	ngmodels "github.com/grafana/grafana/pkg/services/ngalert/models"
+
+	"github.com/grafana/grafana/pkg/api/response"
+	"github.com/grafana/grafana/pkg/models"
+)
+
+// listAlertInstancesEndpoint handles GET /api/alert-instances.
+func (api *API) listAlertInstancesEndpoint(c *models.ReqContext) response.Response {
+	cmd := ngmodels.ListAlertInstancesQuery{DefinitionOrgID: c.SignedInUser.OrgId}
+
+	if err := api.Store.ListAlertInstances(&cmd); err != nil {
+		return response.Error(500, "Failed to list alert instances", err)
+	}
+
+	return response.JSON(200, cmd.Result)
+}