Prevent infinite recursion by calling get_cart_from_session once

Closes woocommerce#7852

A check was aded to prevent get_cart() usage before wp_loaded so all WC
components have a chance to load prior to the cart.

This should solve the edge-case recursion bug by first checking if the
woocommerce_cart_loaded_from_session action has already run. This is
triggered when loading the cart for the first time.

includes/class-wc-cart.php

@@ -681,9 +681,11 @@ public function get_undo_url( $cart_item_key ) {
 		 */
 		public function get_cart() {
 			if ( ! did_action( 'wp_loaded' ) ) {
-				$this->get_cart_from_session();
 				_doing_it_wrong( __FUNCTION__, __( 'Get cart should not be called before the wp_loaded action.', 'woocommerce' ), '2.3' );
 			}
+			if ( ! did_action( 'woocommerce_cart_loaded_from_session' ) ) {
+				$this->get_cart_from_session();
+			}
 			return array_filter( (array) $this->cart_contents );
 		}