Update EDD tracking to include `item_id` and `price`

[zutigrm]

Feature Description

Existing add_to_cart and purchase events should be updated to include item_id for each item in the cart/purchase items list, as well as price.

EDD add_to_cart event can be also update a bit to pull value from the cart total from the details object directly, instead of using individual item's value

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Implementation Brief

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