test suite for hyperparameter optimizers

[shinnar]

There is an existing ad-hoc set of tests for our our optimizers.
We should factor out a standard set of tests that are generic over the choice of optimizer, that can be re-used/run against each optimizer. This can then be used as a test suite for new optimizers, including ones that live in other repositories (such as NSGA-II based optimizer recently added to lale-gpl)

[shinnar]

This should include tests for the expected format of the return value from the summary method