Refactor the Product form

[naydav]

Full context in documentation

[HLD] Inconsistent saving of Stock Data

Description

Currently, the product form sends data to the server in two keys:

1. stock_data
2. quantity_and_stock_status
   After refactoring, the form should send data in a single field.

The best way is to keep the data consistent with Magento WebAPI:

[
    ProductInterface::EXTENSION_ATTRIBUTES_KEY => [
        'stock_item' => [
            StockItemInterface::QTY => 1000,
            StockItemInterface::IS_IN_STOCK => true,
            ...
        ],
    ]

You will also need to update:

• \Magento\CatalogInventory\Ui\DataProvider\Product\Form\Modifier\AdvancedInventory::modifyData