Disambiguate passing multiple datasets to apply

[aguschin]

@mike0sv comment:

it seems that this logic will apply model to multiple datasets in one run. My vision was to apply model once, but using multiple datasets (for example, .fit with X and y)

It seems we need to support both approaches. I had a case in mind when you have a folder with images and want to run your NN on all of them at once.

[mike0sv]

I decided to limit cli capabilities in favor of better UX. User can always call cli multiple times to do multiple infers, and regular models do not have multiple input datasets. For anything more complex api can be used