Preparing for Iron Patch and Sync 2023-11-17

The patch and sync are complete.

Important announcement

We’ve recently made an important update to ROS 2: loaned messages are
now disabled by default. If you don’t know what loaned messages are,
then you can stop reading now. If you are using loaned messages,
continue reading.
We disabled the loaned messages by default to address safety
concerns, as there were instances of shared pointers being unsafely
reused across multiple callbacks. While this adjustment temporarily
limits loaned message capabilities in callbacks, it’s a necessary step to
ensure the reliability and safety of the system. See Disable the loaned messages inside the executor. by clalancette · Pull Request #2335 · ros2/rclcpp · GitHub for more details.
If you understand the risks of using loaned messages and want to enable them,
you can set ROS_DISABLE_LOANED_MESSAGE=0 in the environment before launching your nodes.
Rest assured, we’re exploring options to safely reintroduce this feature in the future. Your
understanding and support in this matter are greatly appreciated.