APM/Pixhawk I2C: Read EzUHF RSSI+LQ

Feature request: Can we read EzUHF RSSI+LQ over the I2C bus? This would be a great enhancement and would solve a lot of PWM methods to do the same, and would make minmosd-extra really shine. See below videos for examples:

https://www.youtube.com/watch?v=TJioJOXqoXQ

https://www.youtube.com/watch?v=kOqGUdVWp-g

The issue names no files, tests, or entry points. Start by locating the APM/Pixhawk I2C integration and EzUHF handling, then determine the expected RSSI and LQ data path from the linked examples. Done means the requested values can be read over I2C without relying on the PWM methods described.

Written by the indexing model from the issue text.