SQL datasources: Consistent interval handling (#78517)

sql: apply the received interval-value

pkg/tsdb/mssql/mssql_test.go

@@ -319,7 +319,8 @@ func TestMSSQL(t *testing.T) {
 							JSON: []byte(`{
 								"rawSql": "SELECT $__timeGroup(time, $__interval) AS time, avg(value) as value FROM metric GROUP BY $__timeGroup(time, $__interval) ORDER BY 1",
 								"format": "time_series"}`),
-							RefID: "A",
+							RefID:    "A",
+							Interval: time.Second * 60,
 							TimeRange: backend.TimeRange{
 								From: fromStart,
 								To:   fromStart.Add(30 * time.Minute),