Revoke and Remove Tokens on Uninstall

[n7studios]

Summary

When the user uninstalls the Kit for WooCommerce Plugin from their WordPress Site:

• Revokes the access and refresh tokens by calling the oauth/revoke endpoint
• Removes the v3 API Key, v3 Secret, v4 Access Token, v4 Refresh Token and v4 Token Expires settings from the database.

https://developer.wordpress.org/plugins/plugin-basics/uninstall-methods/ defines "Uninstall" as:

A plugin is considered uninstalled if a user has deactivated the plugin, and then clicks the delete link within the WordPress Admin.

Testing

• testPluginDeletionRevokesAndRemovesTokens : test that uninstalling (deleting) the Plugin revokes and removes tokens.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)