add "map vs flatMap" perf test case
add "map vs flatMap" perf test case

AyaMorisawa/kefir,AyaMorisawa/kefir,hsavit1/kefir,lautis/kefir,pixelpicosean/kefir,AgentME/kefir,elsehow/kefir,kelsadita/kefir,hsavit1/kefir,kelsadita/kefir,pixelpicosean/kefir,AgentME/kefir,elsehow/kefir,lautis/kefir