[SYCL] deprecate ext_oneapi_get_last_event and ext_oneapi_set_external_event

Author: igchor

sycl/doc/extensions/experimental/sycl_ext_oneapi_in_order_queue_events.asciidoc renamed to sycl/doc/extensions/deprecated/sycl_ext_oneapi_in_order_queue_events.asciidoc

@@ -3557,10 +3557,14 @@ class __SYCL_EXPORT queue : public detail::OwnerLessBase<queue> {
 
   ur_native_handle_t getNative(int32_t &NativeHandleDesc) const;
 
+  __SYCL_DEPRECATED("To get event representing last operation use"
+                    "ext_oneapi_submit_barrier()")
   std::optional<event> ext_oneapi_get_last_event() const {
     return static_cast<std::optional<event>>(ext_oneapi_get_last_event_impl());
   }
 
+  __SYCL_DEPRECATED("To specify external dependency, use handler::depends_on() "
+                    "or submit a barrier using ext_oneapi_submit_barrier()")
   void ext_oneapi_set_external_event(const event &external_event);
 
 private: