Split ROS 1 -> 2 C++ page into a reference page and a tutorial page

[sloretz]

This splits the C++ ROS 1 to 2 migration page into two pages:

• A tutorial page, which is good for beginners to migrating from ROS 1 to ROS 2
• A reference page, which is good for someone actively migrating their package and wanting to CTRL+F how to do something

The tutorial content is unchanged except for:

• Added an intro, prerequisites, and conclusion sections
• Removed the sections about how to build and run the ROS 1 code because it's not easy to require both a working ROS 1 and a working ROS 2 installation on the same machine
• Changed ^^^^ to ---- in a couple headings to put them on the same level as Prerequisites.

[github-actions[bot]]

HTML artifacts: https://github.com/ros2/ros2_documentation/actions/runs/11117920873/artifacts/1998717552.

To view the resulting site:

1. Click on the above link to download the artifacts archive
2. Extract it
3. Open html-artifacts-4779/index.html in your favorite browser