Dockerfiles: Fix issues in the runtime environment

The default implementation of the ROS middleware set by ROS2 Humble and
by Autoware 2023.10 are different. The current version of the
actuation_message_converter package requires the ROS2 default to work,
so ensure the bash environment is set correctly for the user.

The gdown version shipped in the base Autoware image has a bug that
prevents proper usage in the reproduction of the demo. Pin its version
to the first next version that includes the fix.

Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>