Add tracking of the notifications global state

[xristos3490]

Description

This PR adds tracking of the global notification reminders state of a store within the WC_Tracker snapshot.

How to test this PR

1. Install a snippet to run the data fetching function on init. Like the following:

add_action( 'init', function() {
    error_log( 
        print_r(
            WC_Subscriptions_Tracker::add_subscriptions_tracking_data( array( 'extensions' => array( 'wc_subscriptions' => array() ),
            true,
        )
    );
}

2. Monitor server logs.
3. Ensure that the newly added setting is working as expected while you change the global setting.

Product impact

• Added changelog entry (or does not apply)
• Will this PR affect WooCommerce Subscriptions? yes/no/tbc, add issue ref
• Will this PR affect WooCommerce Payments? yes/no/tbc, add issue ref
• Added deprecated functions, hooks or classes to the spreadsheet

[peterfabian]

The info gets included and reflects the setting correctly ✅ . Thanks!