Add the watchdog timer as our first asyncio component

[nateinaction]

Description

As a flight software engineer
I want to have an established pattern for running multiple tasks at a time
So that I can adopt the pattern for other components moving forward

The watchdog is sufficiently isolated component that it might be a good candidate for an initial and simple asyncio implementation.

Acceptance Criteria

• watchdog_pet() is only called in one location (possibly a while loop in main.py)
• remove additional calls to watchdog_pet() in main.py and safe_sleep()
• watchdog_pet() is running asynchronously in the background

Technical Details

• @Mikefly123 does a good job explaining what the hardware watchdog is and how it works on Ping the Hardware Watchdog GPIO Pin fprime-proves#27
• Not the same asyncio library but this video shows what it might be like to write a simple program using asyncio for micropython: https://www.youtube.com/watch?v=5VLvmA__2v0
• I could be wrong but suspect successful completion of this task will involve importing asyncio from lib in main.py and pysquared.py then modifying main.py and the following lines watchdog_pet
• Calls to remove in safe_sleep

[yudataguy]

Let me take a stab at this

[Mikefly123]

It should be relatively straight forward to implement! I think main thing to figure out will be how to reconcile having asyncio awaits in multiple difference locations in the code. We originally only had it implemented in main and it worked fine, but when we transitioned to the new adafruit_RFM radio library the implementation broke because the new radio library also has await calls that seemed to cause a race condition with main.