Add concurrent control and test to verifier

[aweisberg]

Test plan - Added unit tests

In some cases it is useful to run control and test queries concurrently. It can ensure long running queries are run at roughly the same time of day so the ambient load and queuing is the same, and it can also allow the overall latency of a test run to be lower.

== RELEASE NOTES ==

Verifier Changes
* Add support to verifier for running control and test queries concurrently through config `concurrent-control-and-test` and test property.