In order to allow observation of ServerClosedEvent and TopologyClosedEvent (PHPC-2023), php_phongo_pclient_destroy no longer clears APM callbacks unless PHP is already in request shutdown. This allows those SDAM events to be observed for request-scoped clients; however, they still cannot be observed for persistent clients since those are freed during GSHUTDOWN.

With that change, it will now be possible to observe command monitoring events for commands issued during mongoc_client_destroy() (e.g. endSessions) for request-scoped clients. This will entail swapping the order in which Managers and clients are unregistered in php_phongo_manager_free_object.