MSI: assignStatusToProduct for multi stocks is getting the wrong stock id

@nmalevanec is already working on this.

Since Apr 14, 2020.

Hello,

I think there is an error when magento try to get the stock id. Current store is selected instead of selecting product's store which leads to product availability errors when I try to create an order from a rma's order in admin.

### Preconditions (*)

1. magento/project-enterprise-edition 2.3.0
2.

### Steps to reproduce (*)

1. Enable multi stocks
2. Set quantity from product to stock A = 0 and stock B = 10
3. Store 1 should use stock A and Store 2 should use stock B
2. Create a product from an order item
2. Set product store id from order store id which was stock B
3. Check isSalable

```
$product = $this->_objectManager->create(Product::class)
->setStoreId($order->getStoreId())
->load($orderItem->getProductId());

if ($product->isSalable()) {
$unavailableProducts[] = $orderItem->getSku();
}
```

### Expected result (*)

1. isSalable should return true

### Actual result (*)

1. isSalable is false
2. Plugin/CatalogInventory/Helper/Stock/AdaptAssignStatusToProductPlugin.php is looking for stock id of current website which is not the website from the product.

So product availability in admin is calculate upon wrong website.

Which I did to try to fix it :
- I disabled plugin adapt_add_stock_status_to_products + adapt_assign_status_to_product
- I created new plugin which send "storeCode" through "Model\GetStockIdForCurrentWebsite"

```
$storeCode = '';
if (!is_null($product->getStore())) {
$storeCode = $product->getStore()->getCode();
}
$stockId = $this->getStockIdForCurrentWebsite->execute($storeCode);
```

- I override Model\GetStockIdForCurrentWebsite.php

```
public function execute($websiteCode = ''): int
{
if(empty($websiteCode)) {
$websiteCode = $this->storeManager->getWebsite()->getCode();
}

$stock = $this->stockResolver->execute(SalesChannelInterface::TYPE_WEBSITE, $websiteCode);
$stockId = (int)$stock->getStockId();

return $stockId;
}
```