CMAES optimisers can silently make parameters be OOB

[YonatanGideoni]

Bug description

CMAES, being currently implemented as an unconstrained optimiser, can sometimes give (and internally use) parameters that are out-of-bounds (OOB). No error or warning is raised so this fails silently.

To Reproduce

MWE shown in this .py file: https://drive.google.com/file/d/1nc6D195WnUTvDr-K9Sn7gvzar_67sYsE/view?usp=sharing

Expected behavior

For the optimiser not to give OOB results and if there are such results then for a warning/error to be raised.

Environment

• OS: Windows 10
• Python Version: 3.8
• c3-toolset Version: latest

Additional context

There are two solutions that need to be implemented here:

1. Following the example in https://github.com/CMA-ES/pycma/blob/master/notebooks/notebook-usecases-constraints.ipynb, make our CMAES implementation be constrained.
2. Make this not be a silent failure - have it raise a warning/error. This should deal with such cases also in the future and with other such existing optimisers, if there are any.

[YonatanGideoni]

It seems that the solution given in (1) in practice doesn't work all that well, nor does artificially making the function be in an infinite well such that infeasible solutions have a cost of $\infty$. As #236 at least makes this not be a silent failure and currently there does not seem to be a reasonable way to make CMAES be constrained, I will mark #236 as closing this issue.