Add SearchParameters in ParameterSpace::explore

[jbajic]

Enable passing SearchParameters to the ParameterSpace::explore function so different configurations can be passed to get different results for autotuning or to even set up different iteration mechanisms in some cases (e.g., IVF indexes have InvertedListsIterator where we can control how to iterate and might have expectations on getting the proper SearchParameters structure)

This is about solving the problem when the index has params == nullptr it uses nProbe from the index otherwise, it uses the nProbe from params. So when we pass params to the explore function, not purely for optimizing but for giving the proper context down to the iterators, we need to enable reading these optimization params from the params as well.

[meta-codesync]

@mnorris11 has imported this pull request. If you are a Meta employee, you can view this in D107264346.