[metrics] Add metrics for create and delete op time

Add server-level statistics to track the time consumption of
create tablet and delete tablet operations.
The addition of monitoring items will aid in historical issue
tracking and analysis, as well as facilitate the configuration
of monitoring alarms.

Change-Id: I02bd52013caa94a33143cb16ff3831a49b74bac4
Reviewed-on: http://gerrit.cloudera.org:8080/21316
Tested-by: Kudu Jenkins
Reviewed-by: Alexey Serbin <alexey@apache.org>
4 files changed