Adds priority to enhanced catalog attributes and display them as per their priority

[ibndawood]

Changes proposed in this Pull Request:

The enhanced attributes in the product edit are not assigned a priority. This results in related attributes appearing randomly instead of together, as shown in the screenshot below.

It is expected that the product dimensions such as length, width, height, and depth should appear together. This PR loops through recommended attributes and assigns a priority index. We'll then sort the recommended attributes based on the priority.

• Do the changed files pass phpcs checks? Please remove phpcs:ignore comments in changed files and fix any issues, or delete if not practical.

Screenshots:

After this PR:

Detailed test instructions:

1. Install, activate, and connect Facebook for WooCommerce.
2. Navigate to Products > All Products and click on Edit to open the product editor.
3. In the Product data metabox, choose the Facebook tab.
4. For Google Product Category field, choose a category that has measurements as attributes. A list of all category and their respective attributes can be found here: https://github.com/woocommerce/facebook-for-woocommerce/blob/develop/bin/fb_google_category_to_attribute_mapping.json
5. Verify that the category specific fields are in order: Length, Width, Height, Depth, other measurement attributes and others. Please note that not all measure fields are available for all attributes. The order should be for whatever attributes are available.

Additional details:

Related forum issue: https://wordpress.org/support/topic/ui-issues-2/

Changelog entry

Add - Priority to enhanced catalog attributes and display as per priority.