feat(site-kit): add logging when site kit disconnects

[chickenn00dle]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Closes https://app.asana.com/0/1206274567818686/1207849727795693

This PR adds newspack manager logging whenever we detect a site kit disconnection via:

1. the delete_option_{option} hook for the has_connected_admin option.
2. the update_user_metadata hook for when the disconnected_reason user meta is updated.
3. a cron job that checks to see if there are any admin connection daily

For the first two cases, a backtrace is included in the log. For the final one, we simply log a message.

How to test the changes in this Pull Request:

1. Tunnel your local site so your URL is public and connect Google Site Kit
2. Access admin via the local url (not the public one) to trigger a Site Kit disconnect.
3. Using something like WP-Crontrol, verify a new daily newspack_googlesitekit_disconnection_logger cron event is present.
4. Trigger the event and check for a log file in /tmp/ like /tmp/2024-XX-XX-newspack_googlesitekit_disconnect
5. Verify the following logs are present:

• No active Google Site Kit connections found
• Google Site Kit has been disconnected for all admins
• Google Site Kit has been disconnected with reason REASON

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[leogermani]

Beautiful.

I did a small change to bum the log level for the cron check so we can get more proactive alerts