19520 improve navigation experience a11y

[pls78]

Context

• We want to enhance the accessibility of our new Settings UI by allowing screen readers to notify users when they change section.

Summary

This PR can be summarized in the following changelog entry:

• Allows screen readers to notify the user when s/he navigates to a new section in the Settings page.

Relevant technical choices:

• The react-aria-live package has been favored over @wordpress/a11y speak because it is implemented in a way which plays nicer with our Settings UI (i.e. by using React context takes care of reading things just once when it's needed).
• When the screen reader encounters a section containing info or warning boxes will give precedence to their content before announcing the section. This is foreseen behavior.

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Activate a screen reader
  • If you're on MacOS you can activate the VoiceOver screen reader by pressing (fn)+Cmd+F5
  • Tip: by pressing ctrl you can interrupt the message that is currently being spoken
• Navigate to Yoast SEO -> Settings
• Navigate through some sections of the Settings page and verify that, at each section change, that section is being announced with the format: section name + Settings + Yoast SEO

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

• Please verify which is the suggested browser supported by your OS for what concerns accessibility (for MacOS is Safari)

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:

• Nothing more needs to be tested.

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 #19520

[igorschoester]

CR && AC ✅