SQL data sources: Convert to return data frames (#32257)

Convert SQL data sources to return data frames.

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
Co-authored-by: Will Browne <will.browne@grafana.com>
Co-authored-by: Hugo Häggmark <hugo.haggmark@gmail.com>

pkg/services/sqlstore/sqlstore.go

@@ -510,6 +510,14 @@ func IsTestDbPostgres() bool {
 	return false
 }
 
+func IsTestDBMSSQL() bool {
+	if db, present := os.LookupEnv("GRAFANA_TEST_DB"); present {
+		return db == migrator.MSSQL
+	}
+
+	return false
+}
+
 type DatabaseConfig struct {
 	Type             string
 	Host             string