Create the llms.txt settings page with some first elements

[leonidasmi]

Context

Summary

This PR can be summarized in the following changelog entry:

• Creates the llms.txt settings page.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Go to Settings->Site features and confirm that there's no llms.txt feature card anymore there
• Go to Settings->Advanced->llms.txt and see that it contains the basic structure of the designs
  • basically the first two sections
  • (the complete designs will be implemented later on)
• Click to enable the feature and confirm you get the By saving your changes we will generate your llms.txt file. alert, until you save the change.
• Once the change is changed and the feature is enabled, you will see the button getting activated.
  • Once it does, it points to the llms.txt file.
  • Once the feature is enabled, the llms.txt page selection section gets enabled
    • (actually when the feature is disabled, the section is still enabled, only the radio buttons are the ones that get disabled. this is exactly how other parts of our settings work)
• Save all combinations of the settings present here and refresh to see them being perserved.
• Refresh the page while the feature is enabled and working properly
  • You will see in console the hasGenerationFailed false & generationFailureReason entries
  • Note for QA: Those entries will stay there until we implement the error handling UX, so ignore if that's already done by the time you test this PR
• Make a manual edit in the file and save it. This will fail the next regeneration
  • Use the WP crontrol plugin to trigger the wpseo_llms_txt_population scheduled action. This will try to regenerate the file but will fail
  • Refresh the settings page and confirm that in console you get the hasGenerationFailed true & generationFailureReason not_managed_by_yoast_seo entries.
  • Note for QA: Those entries will stay there until we implement the error handling UX, so ignore if that's already done by the time you test this PR

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• Changes should be tested on different browsers
• Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• I have added unit tests to verify the code works as intended.
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label.
• I have added my hours to the WBSO document.

Fixes #

[coveralls]

Pull Request Test Coverage Report for Build 7cb160fe1a230dd54152d8ddb764039c34b59769

Details

• 3 of 42 (7.14%) changed or added relevant lines in 6 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 53.857%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/integrations/settings-integration.php	1	2	50.0%
packages/js/src/settings/routes/site-features.js	0	2	0.0%
packages/js/src/settings/store/llms-txt.js	0	7	0.0%
src/llms-txt/application/configuration/llms-txt-configuration.php	0	10	0.0%
packages/js/src/settings/routes/llms-txt.js	0	19	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/integrations/settings-integration.php	1	26.14%

Totals
Change from base Build 2cb1fe5a14d41829c8bcc092ff6205ff9c843724:	-0.03%
Covered Lines:	30490
Relevant Lines:	57581

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💛 - Coveralls

[vraja-pro]

CR & AC ✅