Add release note for WorkProcessorOperator stats.
Add release note for WorkProcessorOperator stats.

erichwang/presto,wyukawa/presto,11xor6/presto,smartnews/presto,ebyhr/presto,erichwang/presto,electrum/presto,martint/presto,Praveen2112/presto,ebyhr/presto,smartnews/presto,wyukawa/presto,smartnews/presto,losipiuk/presto,erichwang/presto,Praveen2112/presto,treasure-data/presto,martint/presto,dain/presto,electrum/presto,treasure-data/presto,treasure-data/presto,losipiuk/presto,smartnews/presto,hgschmie/presto,dain/presto,erichwang/presto,dain/presto,wyukawa/presto,Praveen2112/presto,electrum/presto,erichwang/presto,electrum/presto,ebyhr/presto,martint/presto,hgschmie/presto,11xor6/presto,electrum/presto,hgschmie/presto,martint/presto,martint/presto,11xor6/presto,ebyhr/presto,losipiuk/presto,treasure-data/presto,11xor6/presto,dain/presto,losipiuk/presto,hgschmie/presto,wyukawa/presto,Praveen2112/presto,11xor6/presto,Praveen2112/presto,ebyhr/presto,dain/presto,treasure-data/presto,smartnews/presto,wyukawa/presto,treasure-data/presto,losipiuk/presto,hgschmie/presto