Allow setting of "all" prices

[TheKeymaster]

Purpose

Right now you would need to go through all prices if you built them dynamically just to get the values and set them again like:

/** @var Price[] $prices */
foreach ($prices as $price) {
    foreach ($price->getValues() as $usergroup => $priceValue) {
        $this->xmlItem->addPrice($priceValue, $usergroup);
    }
}

Approach

Create method \FINDOLOGIC\Export\Data\Item::setAllPrices which allows setting an array of Prices. We already have methods for setAllOrdernumbers and setAllImages which allow easy setting of properties.

Open Questions and Pre-Merge TODOs

• [x] composer lint and composer fix was executed.
• [x] Tests were written and pass with 100% coverage.
• [x] ~A issue with a detailed explanation of the problem/enhancement was created and linked.~ Not really relevant.