Beef up pytest to allow for a benchmarking option

[rocky]

We can enhance the pytests to facilitate benchmarking the tests.

While it is true that benchmarking and testing are separate, a simple change here can give some idea.

Basically most of the pytests funnel through a few helper routines. So that would test an environment setting and accumulate timings if that's set.

[TiagoCavalcante]

@rocky I think it is already fixed by TraceBuiltins.

[rocky]

Yes, benchmarking in another repo is much better here.