add memory counter to servicelab_benchmarks
add memory counter to servicelab_benchmarks

Summary: This diff added memory counter to benchmark and used new [servicelab feature](https://fb.workplace.com/groups/perflab.radar/permalink/4206055712776345/) to track it.

Reviewed By: yfeldblum

Differential Revision: D23686578

fbshipit-source-id: b7dbc31098adafc23adfde34fc4815a3d80d65a3

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift