Add geolocation-based filtering

[stklcode]

Feature request from WP support forums: https://wordpress.org/support/topic/great-feature-request/

Introduce a feature to white- or blacklist requests from certain countries from tracking.

To achieve this, a geolocation service has to be integrated and processed during live filter - cron cleanup is not possible here because the IP is not saved.

Such service might be MaxMind GeoIP2 which provides a nice PHP API¹. Keep in mind the latest changes for database usage².

[1] https://maxmind.github.io/GeoIP2-php/
[2] https://blog.maxmind.com/2019/12/18/significant-changes-to-accessing-and-using-geolite2-databases/