Prevent showing tasks about content SEO if not applicable

[leonidasmi]

Context

Summary

This PR can be summarized in the following changelog entry:

• Hides tasks about content's SEO if indexables or the SEO analysis feature are disabled.

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:

• Check the /wp-json/yoast/v1/get_tasks GET request and confirm that you get the improve-content-seo-post task and its children (search for improve-content-seo- in the response and you will see them)
• Delete transients: wp transient delete --all
• Disable the indexables via the add_filter( 'Yoast\WP\SEO\should_index_indexables', '__return_false' ); filter and repeat the GET request
  • This time you won't see the improve-content-seo-post task and its children (search for improve-content-seo- in the response and you will get no results
• Delete transients: wp transient delete --all
• Remove the add_filter( 'Yoast\WP\SEO\should_index_indexables', '__return_false' ); filter
• Disable the SEO analysis feature from Yoast settings and repeat the GET request
  • This time you won't see the improve-content-seo-post task and its children (search for improve-content-seo- in the response and you will get no results
• Delete transients: wp transient delete --all
• Remove the add_filter( 'Yoast\WP\SEO\should_index_indexables', '__return_false' ); filter
• Enable the SEO analysis feature from Yoast settings
• Disable the SEO analysis feature for your user only from the user profile and repeat the GET request
  • This time you won't see the improve-content-seo-post task and its children (search for improve-content-seo- in the response and you will get no results

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:

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.
• This PR also affects Yoast SEO for Google Docs. I have added a changelog entry starting with [yoast-doc-extension], added test instructions for Yoast SEO for Google Docs and attached the Google Docs Add-on 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.
• I have run grunt build:images and commited the results, if my PR introduces new images or SVGs.

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 310696eff0c2e523dd196fe56dc732b967f3d44f

Details

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 52.99%

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Totals
Change from base Build 0b8a6e27770138bf87283d53e22963839ec6299f:	-0.5%
Covered Lines:	32549
Relevant Lines:	61460

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💛 - Coveralls

[FAMarfuaty]

LGTM! 🙌🏽