Revert "Test datasource: Returns always float values (#34986)" (#35316)

This reverts commit 51afde34bd.

pkg/tsdb/testdatasource/csv_data.go

@@ -183,9 +183,28 @@ func csvValuesToField(parts []string) (*data.Field, error) {
 		return field, nil
 	}
 
-	// Try parsing values as floats
+	// Try parsing values as numbers
 	ok := false
-	field := data.NewFieldFromFieldType(data.FieldTypeNullableFloat64, len(parts))
+	field := data.NewFieldFromFieldType(data.FieldTypeNullableInt64, len(parts))
+	for idx, strVal := range parts {
+		if strVal == "null" || strVal == "" {
+			continue
+		}
+
+		val, err := strconv.ParseInt(strVal, 10, 64)
+		if err != nil {
+			ok = false
+			break
+		}
+		field.SetConcrete(idx, val)
+		ok = true
+	}
+	if ok {
+		return field, nil
+	}
+
+	// Maybe floats
+	field = data.NewFieldFromFieldType(data.FieldTypeNullableFloat64, len(parts))
 	for idx, strVal := range parts {
 		if strVal == "null" || strVal == "" {
 			continue