Topic/plat 6702

This adds ParameterizedSmileModelDiscreateVolatilityFunctionProvider which is a type of DiscreteVolatilityFunctionProvider, but was missed out of the previous PR (topic/PLAT-6701) because it is a relativity involved class. ParameterizedSABRModelDiscreteVolatilityFunctionProvider is a concrete implementation which just implements two small abstract methods.
Same as above, explain why, not that it is.