Make benchmark wrapper user configurable

[snimmagadda]

From Tom Kelly on slack: "one thing that would be awesome in sandmark is the ability to configure the benchmark wrapper that collects the stats. Right now we have orun -o <output> -- <program-to-run> <program-arguments> which is static in the dune file. It would be nice if we could have the user configure in a central place <command> -o <output> -- <program-to-run> <program-arguments>. This can be powerful as you can then get off the shelf wrappers in there like ocperf.py and strace. It should also allow the user to define the arguments they want to pass to perf. For example they could record all the benchmarks for a given target."

[ctk21]

We have this capability with the wrappers parameter in run_config.json