Add notice when upgrading to plugin version >= 3.0.0 (3191)

[burdulixda]

This PR introduces a notice that is hooked into the “update notice” when an update is available for the PayPal Payments plugin, and the version is 3.0 or higher.

• The notice should inform users of potentially significant changes in the 3.0 update.
• The notice advises users to review the update details before proceeding.
• The notice is prominently displayed in the WordPress admin interface on the plugins page, directly below the regular update notice.

Screenshot below or reference:

The wording of the notice text:

Warning: WooCommerce PayPal Payments version 3.0.0 contains significant changes that may impact your website. We strongly recommend reviewing the changes and testing the update on a staging site before updating it on your production environment.

Acceptance Criteria

• GIVEN PayPal Payments is installed in a version below 3.0
• WHEN an update to version 3.0 or newer is available
• THEN an warning notice is displayed on the plugins.php and the PayPal Payments settings pages to warn the user about the potential impact of the available update.