Alerting: introduce AlertQuery in definitions package (#63825)

* copy AlertQuery from ngmodels to the definition package
* replaces usages of ngmodels.AlertQuery in API models
* create a converter between models of AlertQuery
---------

Co-authored-by: Alex Moreno <alexander.moreno@grafana.com>

pkg/services/ngalert/api/api_provisioning_test.go

@@ -1021,13 +1021,13 @@ func createTestAlertRule(title string, orgID int64) definitions.ProvisionedAlert
 		OrgID:     orgID,
 		Title:     title,
 		Condition: "A",
-		Data: []models.AlertQuery{
+		Data: []definitions.AlertQuery{
 			{
 				RefID: "A",
 				Model: json.RawMessage(testModel),
-				RelativeTimeRange: models.RelativeTimeRange{
-					From: models.Duration(60),
-					To:   models.Duration(0),
+				RelativeTimeRange: definitions.RelativeTimeRange{
+					From: definitions.Duration(60),
+					To:   definitions.Duration(0),
 				},
 			},
 		},