refactor: migrate protected branch fields into one json column and support system users (#39735)

1. migrate protected branch fields into one json column
2. use the dropdown list for push/force-push user selection, and Actions
user can be added into the list now.

modelmigration/base/db.go

@@ -518,3 +518,20 @@ func ModifyColumn(ctx context.Context, x EngineMigration, tableName string, col
 func Iterate[Bean any](ctx context.Context, cond builder.Cond, f func(ctx context.Context, bean *Bean) error) error {
 	return db.Iterate(ctx, cond, f)
 }
+
+func EngineTransaction(x EngineMigration, f func(Session) error) error {
+	sess := x.NewSession()
+	defer sess.Close()
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+	err := f(sess)
+	if err != nil {
+		return err
+	}
+	return sess.Commit()
+}
+
+func IterateTableByColumn[Bean any](ctx context.Context, x EngineMigration, sess Session, colName string, cond builder.Cond, f func(ctx context.Context, bean *Bean) error) error {
+	return db.IterateTableByColumn(ctx, x, sess, colName, cond, f)
+}