Refactor project to be a normal ROS package

[felixdivo]

This was required for #23 / ros/rosdistro#39892.

It also switches from black to ruff format and activates two previously broken test cases. Also restores installability on CI for ROS Rolling.

[felixdivo]

I don't really understand how to fix the error here: https://github.com/felixdivo/ros2-easy-test/actions/runs/8659687762/job/23746089747?pr=33 ...

[Timple]

Perhaps because extras_require lists a lot of dependencies. These will (but shouldn't be) pip installed?

I would actually just pick one release method. Remove all pip related stuff and create a nice ros package.

[felixdivo]

Well, pip is still required to install makefun (sadly not available via package.xml/Ros Index). But aside from that, installing it for normal usage works without it. Installing for development needs more dependencies, so there you'd still require pip.