Support for sdformat14 and Gazebo Harmonic

[quarkytale]

Once Rolling rolls over for ROS 2 Jazzy, we'll default to using sdformat14.

How should we handle branches in sdformat_urdf? Currently, there's a galactic and a ros2 branch, where the former supports Galactic and everything below. So one option is creating an iron branch and updating ros2 to support newer defaults.

@sloretz How are things typically done in the ROS 2 ecosystem or any other more preferable options?

CC: @azeey

[sloretz]

How are things typically done in the ROS 2 ecosystem or any other more preferable options?

I think the approach that's become recommended is to make a rolling branch, and then branch off that as distros are released. The version of gazebo to be supported on each ROS distro is specified by by REP 2000.

I'd recommend the following goals:

• rolling branch supports Gazebo Harmonic
• iron branch supports Gazebo Fortress
• humble branch supports Gazebo Fortress.

If we don't have the time for all those goals, then I'd recommend the priority being updating Rolling first, then Humble since it's LTS, and lastly Iron as a nice to have.

I think we could get there by doing the following:

1. Create a branch called rolling pointing to the same commit as ros2
2. Update the rolling branch until it supports Gazebo Fortress (unless it does already, then no work to do here)
3. Create a humble branch and an iron branch off of rolling
4. Update the rolling branch to support Gazebo Harmonic

There will be some cleanup work too of updating source branch entries in ros/rosdistro and making bloom releases.