Add support for passing arguments to constructors

[pum1k]

Description

This PR allows passing arguments to plugin constructors. This is done by exposing a new feature of class_loader added in ros/class_loader#223.

[ahcorde]

Pulls: #291
Gist: https://gist.githubusercontent.com/ahcorde/a60864c74e3698258ac6711f38798467/raw/f2aa7f4ba8de68858cc4a421df49836dcf859dbb/ros2.repos
BUILD args: --packages-above-and-dependencies pluginlib
TEST args: --packages-above pluginlib
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18275

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[SteveMacenski]

@ahcorde are you aware this breaks all existing uses of pluginlib? Currently Nav2 does not build due to this, which I highly suspect means that every plugin user would need to update their use of pluginlib to work (since we don't do anything fancy).

I think there either needs to be a workaround for objects without constructor arguments or a detailed migration guide for what updates need to be specifically made. Personally I think a library like this needs a tick-tock migration pattern to give folks time and awareness, but feels to me like this could be done non-disruptively (though this is not my area of expertise)

[pum1k]

@SteveMacenski the Nav2 test is broken, because it depends on private parts of the pluginlib. Code calling the public APIs of pluginlib requires no change.

[SteveMacenski]

Huh - OK - false alarm. Still need to figure out a solution, but feel free to ignore me then 🙃

I thought I saw this show before, but turns out I'm watching a different channel