carbonara: add merge() benchmark
carbonara: add merge() benchmark

Change-Id: I3907c50509fb1136469b95ddc8f60122746dbc6f

gnocchixyz/gnocchi,leandroreox/gnocchi,leandroreox/gnocchi,gnocchixyz/gnocchi,sileht/gnocchi,sileht/gnocchi