executor: migrate test-infra to testify for explain_test (#32307)
executor: migrate test-infra to testify for explain_test (#32307)

close pingcap/tidb#28578
kyle-wang/tidb,kyle-wang/tidb,pingcap/tidb,kyle-wang/tidb,pingcap/tidb,ngaut/tidb,c4pt0r/tidb,c4pt0r/tidb,pingcap/tidb,ngaut/tidb,pingcap/tidb,c4pt0r/tidb,c4pt0r/tidb,pingcap/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,c4pt0r/tidb,kyle-wang/tidb,kyle-wang/tidb,ngaut/tidb,ngaut/tidb,ngaut/tidb,kyle-wang/tidb