Add Python bindings

[srmainwaring]

Desired behavior

Add Python bindings to gz-transport (and gz-msgs).

Alternatives considered

• Use ros_gz bridge and the Python support in ROS / ROS2.

Implementation suggestion

Upstream the bindings for gz-msgs and gz-transport from https://github.com/srmainwaring/gz-python.

Additional context

From time to time there are requests for Python bindings to control the simulation. A number of the requirements can be met by using the messaging infrastructure to control and interact with the simulation.

• https://community.gazebosim.org/t/python-bindings-for-gazebo-ignition/360
• Python bindings to interact with gz-sim gz-sim#1905
• Add overloaded Request for non-blocking calls using abstract types #386

[azeey]

Thanks for the implementation suggestion @srmainwaring. This is something we are hoping to address for Harmonic and having your implementation as a starting point will go a long way. We'd also like to address gazebosim/gz-msgs#113, gazebosim/gz-msgs#36, and gazebosim/gz-sim#494 which might have implications for how we implement this.

[azeey]

This has been implemented in #411