Added a late initialization step. (#14199)

* Added a late initialization step.

This will allow us to migrate code that has been working before plugins are loaded to this later stage where plugin code is available and the autoloader has a way to figure out the latest version of bundled libraries.

* Fix a typo and remove an extra space to clear a phpcs warning.


Co-authored-by: Kim Brown <50059399+kbrown9@users.noreply.github.com>

class.jetpack.php

@@ -570,7 +570,8 @@ private function __construct() {
 			add_action( 'init', array( 'Jetpack_Keyring_Service_Helper', 'init' ), 9, 0 );
 		}
 
-		add_action( 'plugins_loaded', array( $this, 'after_plugins_loaded' )  );
+		add_action( 'plugins_loaded', array( $this, 'after_plugins_loaded' ) );
+		add_action( 'plugins_loaded', array( $this, 'late_initialization' ), 90 );
 
 		add_filter(
 			'jetpack_connection_secret_generator',
@@ -755,6 +756,24 @@ function after_plugins_loaded() {
 		}
 	}
 
+	/**
+	 * Runs on plugins_loaded. Use this to add code that needs to be executed later than other
+	 * initialization code.
+	 *
+	 * @action plugins_loaded
+	 */
+	public function late_initialization() {
+		/**
+		 * Fires when Jetpack is fully loaded and ready. This is the point where it's safe
+		 * to instantiate classes from packages and namespaces that are managed by the Jetpack Autoloader.
+		 *
+		 * @since 8.1.0
+		 *
+		 * @param Jetpack $jetpack the main plugin class object.
+		 */
+		do_action( 'jetpack_loaded', $this );
+	}
+
 	/**
 	 * Sets up the XMLRPC request handlers.
 	 *