[CatalogPromotion] Use Catalog Promotion rule during application

[Zales0123]

Q	A
Branch?	master
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?
Related tickets	based on #13001
License	MIT

[GSadee]

Thank you, Mateusz! 🥇

[lchrusciel]

Won't it work?

Suggested change

	/** @var string $variantCode */
	foreach ($configuration as $variantCode) {
	/** @var ProductVariantInterface|null $variant */
	$variant = $this->productVariantRepository->findOneBy(['code' => $variantCode]);
	if ($variant === null) {
	continue;
	}
	if (!in_array($variant, $variants)) {
	$variants[] = $variant;
	}
	}
	return $variants;
	return $this->productVariantRepository->findBy(['code' => $configuration]);