REF: Unify creation of dataframe for C and Python parser engines
We should unify the process of creating the dataframe from index,names,data for the C and Python engines. This should be done after the pyarrow engine is merged, and will help get rid of some code nested within an if statement. Ideally, we make a method on ParserBase, and call that in the C and Python engine read code so that read always returns a DataFrame now.