Prevent admins to be able to view carousel in shops

[chahmedejaz]

What? Why?

• Closes Prevent admins to be able to display carousel in shops #14157

As part of the multiple product images roadmap, the carousel functionality is being developed before backoffice support for managing multiple images is available.

Currently, it is possible for products to have multiple images associated with them through the image settings page, even though this functionality is not intended to be available to users yet. To keep production data aligned with the current user experience, this PR:

1. Adds a data migration that removes secondary images from products, ensuring each product has at most one product-level image.
2. Removes the ability to create additional product images from the product's image page by hiding the "New Image" action.

Users can still replace an existing product image through the product list and image settings page, so there is no change to the intended image management workflow. A new image can only be added through the product list page.

What should we test?

Scenario 1 - Existing product image management

1. Create or open a product that already has an image.
2. Navigate to the product's Images page.
3. Verify there is no New Image button.
4. Edit the existing image.
5. Upload a replacement image and save.
6. Verify the image is updated successfully.

Scenario 2 - Product without an image

1. Create or open a product with no image.
2. Navigate to the product's Images page.
3. Verify the "no images found" state is displayed.
4. Verify there is no option to create an additional image from this page.
5. From the product list, upload an image for the product.
6. Verify the image appears correctly on the Images page.

Scenario 3 - Migration

1. Run the migration against data containing products with multiple product images.
2. Verify that only the first product image record is retained. i.e. There should not be any visual change of image for the product in the app before and after the migration.
3. Verify that additional product images are removed.

Release notes

Changelog Category (reviewers may add a label for the release notes):

• User facing changes
• API changes (V0, V1, DFC or Webhook)
• Technical changes only
• Feature toggled

Dependencies

Need the following PR to be merged along with this one:

• Show carousel of images when multiple images are available #14337

[chahmedejaz]

This PR is ready for release but we need to wait for its dependent PR. Keeping it in dev test ready for now until the dependent PR is ready for release.

ref: #14364 (comment)