Lowercase query before searching in new settings UI

[nolledgeable]

Context

• Makes the search in new settings UI case insensitive.

Summary

This PR can be summarized in the following changelog entry:

• Makes the search in new settings UI case insensitive.

Relevant technical choices:

• Move from Lodash toLower to string.toLocaleLowerCase for locale specific lowercasing.
• Added a safeToLocaleLower helper that doesn't throw breaking errors when locale is invalid.
• Added a max width to the Force rewrite titles toggle.

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Open the search in the new settings UI.
• Verify that SEO and seo give you the same search results.
• Verify that XML and xml give you the same search results.
• Verify that section descriptions for post types and taxonomies still contain lowercase post type or taxonomy name:

• Verify that the Force rewrite titles toggle is now the same width as toggles below it. This toggle is only visible in non block themes that don't support the title-tag

Dev only additional test

• On line 411 of settings-integration.php, assign something invalid to the userLocale variable, ie. false or 10. Then verify that above lowercasing fails and you have console errors, but the new settings UI doesn't break.

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 (Block/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.

QA can test this PR by following these steps:

Impact check

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

• Only affects the new settings UI.

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.

Quality assurance

• I have tested this code to the best of my abilities
• 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.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label and noted the work hours.

Fixes #
https://yoast.atlassian.net/browse/DUPP-826

[igorschoester]

CR 🏗️

[igorschoester]

Acc ✅