Thank you @mukeshpanchal27 for the PR. I think there are a few things that can be simplified here. Most importantly, let's remove the additional piece of functionality in the module cards which wasn't required and makes the PR more complicated. I left more specific feedback below. Please let me know if you have any questions for clarification.

@mukeshpanchal27 I left some follow up feedback, mostly minor things to clarify wording. For example, I think we should include in the user-facing message that the modules will be removed in the future, for a sense of urgency.

There's one larger consideration here that we may want to change, which I'm just realizing now:

• You've implemented the migration logic in an AJAX request. While this works well, it comes with the problem that then the whole UI on the page may be outdated (e.g. after other plugins were installed, modules deactivated etc.).
• It will probably be too much effort to fix all the UI throughout the page to reflect those changes. Therefore I would suggest to go with a regular full page refresh and instead of AJAX move the logic to an admin_action_{$action} callback, similar to how the plugin activation and deactivation currently is.
• You should be able to copy the logic pretty much as is, just replace the wp_send_json_error() calls with equivalent wp_die(), and the wp_send_json_success() with a redirect back to the Performance Lab plugin screen.
• Doing that will also drastically simplify this PR: You can probably remove the JS file entirely, and the button can simply be a link to e.g. wp-admin/plugins.php?action=...&_wpnonce=....
• Because this is then a full page reload, we don't have to worry about all other UI on the page, as it will be automatically refreshed after the changes have been made.

Let me know what you think about this, or if you have any follow up questions. For now, it's probably best if you just address the more specific feedback below, and we can discuss the above separately afterwards (e.g. in Slack or in PR comments).

@mukeshpanchal27 I just tested this again, and I think it looks almost ready to merge.

Regarding my feedback in #899 (review), I just now realized that you have a window.location.reload() in the JS, so that works perfectly fine then, and the AJAX with loading spinner still makes for a bit nicer user experience. 🎉

My final bits of feedback are below, after that it should be good to merge from my perspective.

Looks great, thanks @mukeshpanchal27!