Log how long it takes to run a query when collecting metrics

Right now all elastic-recheck queries are using query_string queries
against ElasticRecheck, but if we ever support more options like
multi-line queries or regexp queries, it would be good to know how those
perform relative to the query_string queries, so log it at debug level
when running the CLI to dump metrics.

Change-Id: I8414205b84e347d3305ee8d7e6ac2d4ca18c9818
Merge "Log how long it takes to run a query when collecting metrics"