Add mobile app order attribution source

[layoutd]

Changes proposed in this Pull Request:

Closes #44490.

This PR introduces the "Mobile app" order origin to correctly identify orders created in the Woo Mobile App.

NOTE: This PR will only work after #44496 has been merged and the Order Attribution classes are being loaded properly again. Dependency PR merged ✔️

How to test the changes in this Pull Request:

1. Create an order in the WooCommerce dashboard (/wp-admin/post-new.php?post_type=shop_order).
2. The order should show "Web admin" as the origin in the Orders table ( /wp-admin/edit.php?post_type=shop_order) and Order Edit "Order attribution" metabox (/wp-admin/post.php?post=[ORDER_ID]&action=edit).
3. Update the order metadata value for _wc_order_attribution_source_type to mobile_app.
   Using the WC CLI, for example (insert the order ID and admin user if necessary):

   wp wc shop_order update [ORDER_ID] --user=admin --meta_data='[{"key":"_wc_order_attribution_source_type","value":"mobile_app"}]'
   wp wc shop_order get [ORDER_ID] --user=admin --field=meta_data

4. Confirm that the order shows "Mobile app" as the origin in the Orders table and Order Edit metabox.

Changelog entry

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Significance

• Patch
• Minor
• Major

Type

• Fix - Fixes an existing bug
• Add - Adds functionality
• Update - Update existing functionality
• Dev - Development related task
• Tweak - A minor adjustment to the codebase
• Performance - Address performance issues
• Enhancement - Improvement to existing functionality

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[github-actions]

Test Results Summary

Commit SHA: 50b63f6

Test 🧪	Passed ✅	Failed 🚨	Broken 🚧	Skipped ⏭️	Unknown ❔	Total 📊	Duration ⏱️
API Tests	259	0	0	2	0	261	0m 38s
E2E Tests	313	0	0	8	0	321	7m 27s

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To view the full API test report, click here.
To view the full E2E test report, click here.
To view all test reports, visit the WooCommerce Test Reports Dashboard.

[github-actions]

Hi , @woocommerce/ventures

Apart from reviewing the code changes, please make sure to review the testing instructions as well.

You can follow this guide to find out what good testing instructions should look like:
https://github.com/woocommerce/woocommerce/wiki/Writing-high-quality-testing-instructions

[ibndawood]

Thank you, @layoutd. I followed the test instructions and the PR tests well.