Select problem by type

Internal/temporary PR for review.
This turns out to be least invasive and complex solution. Alternatives were:

* Add `problem_type` class method to every CAPA Input type: results in shotgun change - a couple of lines into ~20 classes.
* Determine problem name by CAPA input class name: some classes support multiple modes (e.g. `checkboxgroup` and `radiogroup`) - results in three/four exceptions to the rule that cover ~20 cases. Plus the rule itself would be a bit non-trivial - something like "split into words by capital letters, remove stopwords (e.g. Input), join by space, but don't split JS"

On the other hand, this approach have no "moving parts" (i.e. trivial logic), localized and does not require using reflection in production code. I'm going to try covering this method with test that would check if all the CAPA input type `tag`s are present, so it would still be robust to changes/additions/deletions of CAPA input types.