get_pricing_steps_for_products: Allow passing Product objects
get_pricing_steps_for_products: Allow passing Product objects

To be more in line with the other methods.

suutari-ai/shoop,hrayr-artunyan/shuup,taedori81/shoop,suutari/shoop,suutari-ai/shoop,suutari/shoop,shawnadelic/shuup,shawnadelic/shuup,hrayr-artunyan/shuup,hrayr-artunyan/shuup,jorge-marques/shoop,shawnadelic/shuup,suutari/shoop,akx/shoop,taedori81/shoop,shoopio/shoop,jorge-marques/shoop,taedori81/shoop,shoopio/shoop,akx/shoop,jorge-marques/shoop,shoopio/shoop,suutari-ai/shoop,akx/shoop