Performance testing the optimization on the tsdb benchmark (last point for cpu only data).

• Will need to add appropriate {meta:1, ts:-1} sort to TSBS query here: https://github.com/gregorynoma/tsbs/blob/master/cmd/tsbs_generate_queries/databases/mongo/devops-naive.go 
• Then look at (lastpoint, AvgLatency) results here: https://evergreen.mongodb.com/task/sys_perf_linux_3_node_replSet_tsbs_query_792eaed783453a5f840112919fc0adb628961d24_22_02_14_22_56_39