Camera Node Multithreading

[nlitz88]

Right now, there is no thread-level parallelism in the camera node. This means that all HTTP requests being made are happening sequentially (unless there is some python async magic happening already that I am not aware of).

What tipped me off to this was adding the timer and publisher for the map images (in addition to the front and rear camera images). When adding the map images, the latency for all the topics gets dragged down to 2 Hz from about 8 Hz.

https://answers.ros.org/question/401066/ros2-how-to-do-multi-threading-subscription-callbacks-spinning-executors/