Add a batch mode that parallelizes counter collection over multiple identical GPUs

[IanBogle]

Is your feature request related to a problem? Please describe.
This feature is related to benchmarks that may not be able to be cut down to a smaller representative problem. Collecting counters in parallel would significantly cut down the profile time.

Describe the solution you'd like
An argument to omniperf profile that allows running several counter collections at a time across multiple identical GPUs

Describe alternatives you've considered

Additional context
Suggested by Shane Fogerty at the SNL hackathon