Automatically provision pilot events

[iandunn]

Broken off of #885

Just like with the wordcamp post type, we'll want a button in for the pilot events post type (#900) that will automatically provision a new site, except it'll be on the events.wordpress.org network.

We'll probably want some of the things from wordcamp-new-site.php, like the permalinks:

wordcamp.org/public_html/wp-content/plugins/wcpt/wcpt-wordcamp/wordcamp-new-site.php

Lines 477 to 483 in f5c385e

	/*
	* Avoids URLs like `narnia.wordcamp.org/2020/2010/06/04/foo`. See `redirect_date_permalinks_to_post_slug()`.
	*
	* If ths ever changes, the link in `stubs/page/sponsors.php may need to be updated.
	*/
	$wp_rewrite->set_permalink_structure( '/%postname%/' );
	delete_option( 'rewrite_rules' ); // Delete because can't be flushed during `switch_to_blog()`.

[iandunn]

Done in 3ea133d and a6fc8bc