Multithreading for PID loops

[Willmish]

• Move the PID loops to separate threads to allow them to run on a different clock to the main loop (as main will update DB once every 5s, and PID may need to update more frequently): https://stackoverflow.com/questions/68174615/python-multithreading-with-pypubsub-and-wx
• Run the PID loops from main.py, make sure they still receive pubsub messages and can send them
• Write a testing script for checking pypubsub messages

Ideas for solution

• Keep calling Sensor.collect() for PID purposes, but do not process by the analysers/DB yet,
• Send out a new pubsub topic (e.g. DB update), which propagates through the PID analysers to the actuators, grabs the current sensor values, sensor IDs, types etc and sends a message for the data_streamers to pick up and send to whatever storage system is currently selected.

Useful materials:

• https://docs.python.org/3/library/concurrent.futures.html
• https://docs.python.org/3/library/threading.html
• https://www.youtube.com/watch?v=IEEhzQoKtQU