More flexible method infer_provider

[hovi]

I want to make my own factory method where I create providers based on provider name and other parameters (like base_url).
I found out, that logic that does it in the library is creating providers with default constructor without possibility to pass anything to it.

PR suggests 2 changes. Either change is enough to add the required flexibility:

• Create function that returns provider class without instantiating it
• Add kwargs parameters to infer_provider that are passed to constructor call