br: disable the batch ddl by default (#31845)
br: disable the batch ddl by default (#31845)

close pingcap/tidb#31835
ngaut/tidb,c4pt0r/tidb,c4pt0r/tidb,pingcap/tidb,kyle-wang/tidb,ngaut/tidb,c4pt0r/tidb,kyle-wang/tidb,pingcap/tidb,pingcap/tidb,kyle-wang/tidb,kyle-wang/tidb,pingcap/tidb,pingcap/tidb,ngaut/tidb,kyle-wang/tidb,c4pt0r/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,ngaut/tidb,ngaut/tidb,kyle-wang/tidb,c4pt0r/tidb