Consolidate `check_list_of_param()` and `validate_params()`

[hfrick]

We only really need one function, but we will give it allow_na and allow_unknown arguments. A possible name is check_param_list() as it should operate on the list of param objects.

The grid functions, which currently call validate_params(), need to then collect the dots in a list first but that's not too much overhead and only have to maintain and remember about one checking function.