Split msg generation from driver nodes for Humble

[adityakamath]

I got errors when trying to build with ROS 2 Humble, and realized that calling rosidl_generate_interfaces and ament_python_install_package in the same package does not work.

So, I split up the message generation into a separate package.

References:
ros2/rosidl_python#141
https://docs.ros.org/en/humble/How-To-Guides/Ament-CMake-Python-Documentation.html

Functionality is as expected, but I have not tested the docker scripts (since I do not have experience there). @naoki-mizuno could you please review the docker part? Are any changes needed in the .bash script? Is the docker directory in the correct place, or should it be in the root directory?

I would prefer to have these changes in a new humble-devel branch, but it should work perfectly well on foxy.

[naoki-mizuno]

I haven't been able to keep up with the latest ROS2 releases, so I really appreciate your help! I'll take a look at it later today, thanks!

[naoki-mizuno]

Thanks for your PR! I was able to test the demo script on a docker environment. I did move the docker directory to the root (plus the .gitignore file was outdated for quite a while so fixed that), and went ahead and created a new humble-devel branch, which now is the default branch. Thanks again for your contribution!

[adityakamath]

Oh awesome, that was quick! :)