Specialize collections.namedtuple #174

I noticed PLS has a specialization for typing.NamedTuple, which is, essentially, collections.namedtuple under the hood. Should not be hard to add handling for the later.

I'd be interested on adding a specialization for collections.namedtuple, but I'd like to understand how to add new specializations. Initially, I though it will be as hard as creating a custom CollectionsModuleInfo: BuiltinModule similar to TypingModuleInfo, but then I found also TypingTypeInfo and its Finalize and TypingTypeInfoFinalizer, and a seemingly simple tasks seems convoluted now.

I'd also gladly work on making this exact task simpler in the future.

BTW, here's a commit, that adds a test case for the desired behavior: losttech@0899a19