Setup Pilot Events network and URL support

[iandunn]

See #884
See #885

This handles the interdependent parts of those issues, which covers everything needed to create sites like events.wordpress.test/barcelona/2023/diversity-day/, and have requests routed appropriately.

Testing

⚠️ Do this in a local environment, since more testing is needed before we test this on a w.org sandbox

• Update your wp-config.php and nginx.conf to be similar to the Docker files in Docker: Add configuration for events.wordpress.org network #912. ( I haven't tested Docker yet, though, so more work may be needed in Update Docker env config for Events network #910 to make it work )
• Manually create sites for events.wordpress.test and events.wordpress.test/vancouver/2023/diversity-day/. You'll probably have to use - instead of / in the path when creating them, but then you can edit them to change to /.
• Add those hostnames to your hosts file
• Rerun mkcert to update your SSL certs with the new domain
• Manually change the site_id for those new sites in the wp_blogs table to be 2
• Update EVENTS_ROOT_BLOG_ID values to match the blog you created above
• Don't activate any plugins. We'll have to do Update WordCamp plugins to work with Pilot Sites #886 and Update WordCamp mu-plugins to work with Pilot Sites #906 before they'll work
• Visit the Vancouver site and make sure all the Core functionality works
• Visit Central and a regular site on the WordCamp network and make sure everything still works

[dd32]

Other than some nitpicks around what field is used for switching between the two, this seems good to me (Untested) and I don't really understand the hesitation of just committing and iterating from there.

[pkevan]

just committing and iterating from there.

That would be my preference here too, as I mention in slack, I can't easily see from the code what is needed or not, and what needs fixing.

[iandunn]

This is deployed to production now, and the root site is working.

Event sites like https://events.wordpress.org/narnia/2023/test-site/ need some nginx updates before they'll work.