Avoid duplicate templates appearing on the Site Editor when the WooCommerce template and the theme template have been customized by the user

[Aljullu]

Changes proposed in this Pull Request:

Fixes #42220.

Blocks #43794.

As mentioned in #42220, if the user modified a WooCommerce templates twice, once using the WooCommerce template as the base and the other time using the theme templates as the base, we ended up with duplicate templates on the list.

This PR fixes that and adds some tests to verify we don't introduce regressions in the future.

How to test the changes in this Pull Request:

1. Activate a theme without WooCommerce templates (ie: Twenty Twenty Four).
2. Make a modification to a WooCommerce template. Ie: add a "Hello world" paragraph somewhere in the Single Product template.
3. Now, switch your theme to a theme with WooCommerce templates (ie: Tsubaki).
4. Make a modification to the same template from step 2. You will probably need to access it via the URL. Ie: /wp-admin/site-editor.php?postId=theme-tsubaki%2F%2Fsingle-product&postType=wp_template&canvas=edit. Note: the theme-tsubaki part of the URL might change depending on the ZIP file name that you uploaded. In case of doubt, go to Appearance > Editor > Templates > Template Catalog and look at the URL.
5. Load the templates list: /wp-admin/site-editor.php?path=%2Fwp_template%2Fall.
6. Verify there is only one template named "Single Product".

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

Message

Avoid duplicate templates appearing on the Site Editor when the WooCommerce template and the theme template have been customized by the user

Comment

[Aljullu]

While this constant is currently only used in one file (template-customization.block_theme.side_effects.spec.ts), my plan is to update template-user-customization.block_theme_with_templates.spec.ts and template-user-customization.block_theme.spec.ts to use it as well.

[github-actions]

Test Results Summary

Commit SHA: 18d70ce

Test 🧪	Passed ✅	Failed 🚨	Broken 🚧	Skipped ⏭️	Unknown ❔	Total 📊	Duration ⏱️
API Tests	259	0	0	2	0	261	0m 37s
E2E Tests	289	0	0	7	0	296	6m 15s

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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 @dinhtungdu,

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

[dinhtungdu]

I can confirm issue is fixed following the testing instruction in my tests. The code also looks good to me. I left a minor but non blocking comment. Approving 🚢