executor: remove Next() function for SelectionExec (#6021)
executor: remove Next() function for SelectionExec (#6021)

* executor: remove Next() function for SelectionExec

c4pt0r/tidb,ngaut/tidb,Nify/tidb,ngaut/tidb,c4pt0r/tidb,ngaut/tidb,pingcap/tidb,kyle-wang/tidb,XuHuaiyu/tidb,kyle-wang/tidb,cosmtrek/tidb,ming-relax/tidb,EvilMcJerkface/tidb,ngaut/tidb,c4pt0r/tidb,pingcap/tidb,mccxj/tidb,XuHuaiyu/tidb,tiancaiamao/tidb,ming-relax/tidb,Cofyc/tidb,mccxj/tidb,qiuyesuifeng/tidb,pingcap/tidb,kyle-wang/tidb,kyle-wang/tidb,kyle-wang/tidb,ngaut/tidb,kyle-wang/tidb,c4pt0r/tidb,wusphinx/tidb,Cofyc/tidb,CodeRushing/tidb,qiuyesuifeng/tidb,pingcap/tidb,ngaut/tidb,cosmtrek/tidb,c4pt0r/tidb,c4pt0r/tidb,pingcap/tidb,wusphinx/tidb,Nify/tidb,tiancaiamao/tidb,pingcap/tidb,coocood/tidb,EvilMcJerkface/tidb,coocood/tidb,CodeRushing/tidb