Problem Config should not use global random state

[TobyBoyne]

The suggested API for random number generation in numpy is to use Generator objects, instead of global state. This is because other code can interfere with global state, causing a lack of reproducibility. Changing the global random state outside of ENTMOOT code leads to inconsistent results.

I think we should have a ProblemConfig.rng attribute that handles all random number generation, for more consistency. I also think ENTMOOT should not be using random.random, instead only using numpy (note, I'm not sure if ENTMOOT does use random.random, but that random state is set in ProblemConfig).