Add a test for worker count metric
Add a test for worker count metric

ethercrow/mzbench,alinpopa/mzbench,moigagoo/mzbench,moigagoo/mzbench,avasenin/mzbench,bks7/mzbench,bks7/mzbench,ethercrow/mzbench,alinpopa/mzbench,avasenin/mzbench,ethercrow/mzbench,moigagoo/mzbench,ethercrow/mzbench,alinpopa/mzbench,moigagoo/mzbench,bks7/mzbench,avasenin/mzbench,alinpopa/mzbench,avasenin/mzbench,bks7/mzbench