[amp story shopping] Set active product data in store service

[processprocess]

Description

When a shopping-tag is clicked:
Add an 'activeProductData' key to SHOPPING_DATA.
Set the value to the shopping data (ShoppingConfigDataDef) of the clicked item.

Example implementation of a handler in amp-story-shopping-tag:

const shoppingData = this.storeService_.get(StateProperty.SHOPPING_DATA);
this.storeService_.dispatch(Action.ADD_SHOPPING_DATA, {
   'activeProduct': activeProductData[product-tag-id]
});

An alternate option would be to send the productData from the click handler, this would remove the get from the click handler.