Feature Description

Follow-up to #651: For any site for which the old module slugs are still set in the option for active modules, an additional UI component should be added to the updated PL settings screen to make it easy, yet explicitly intentional, for the admin user to install and activate the respective standalone plugins with a single click.

This will require defining a mapping between the old module slugs and their standalone plugins, so that the plugin can determine where to point the user.

Requirements

• If any of the module slugs that are already available as standalone plugins are still remaining in the option for active modules, some sort of prompt (e.g. an admin notice) should be displayed on the Settings > Performance screen.
  • The check for whether this prompt needs to be shown should be a reusable function (important for Implement admin pointer to indicate to the user they need to activate the new standalone plugins #653).
  • Which exact modules need to be replaced with their plugins is less important to be reusable, though it could certainly be part of a reusable function too if it makes sense.
• The prompt shown on the screen should include:
  • A brief explanation (1-2 sentences) to the user that they have modules activated which will soon be removed from the Performance Lab plugin, and that they need to instead install/activate the relevant standalone plugins
  • A list of which modules are affected (if it's a single module, we could alternatively consider putting it into the floating text, since a list of 1 item is a bit odd)
  • One of the following:
    • If the current user has the install_plugins and activate_plugins capabilities: A primary CTA button (see below) to migrate the active legacy modules to their respective standalone plugins
    • If the current user lacks any of the two capabilities: A CTA message prompting the user to contact an administrator with access to installing/activating plugins
• When the primary CTA button is clicked, logic (could be implemented with a full page reload/form submission, or AJAX, whatever works best) should be run that:
  • Installs and activates the respective standalone plugins as needed.
  • Deactivates the respective legacy modules.