Changed main storage structure to use union for the filters.
Renamed storage variable passed to the sub functions to avoid confusion with the global static.
Added whitespace to separate logical blocks and added additional comments to make the code more readable.
Restructured derivative filter initialization/update logic.
Cleans up the many static variables into a single structure. Saves ~60 bytes on F3 but far more importantly will allow the support functions to be easily moved to a size optimized file at some later date.
Adds in flight monitoring of the rx frame rate and adapts the filters if the frame rate changes. Primarily to add support for Crossfire with its ability to switch from 150hz to 50hz (and back) under some circumstances. Will work with any protocol - not CRSF specific. So if future receivers add the ability to switch frame rates dynamically the logic should support them.
If the current rx frame rate is more than +-20% from the previously detected rate, then the process will retrain for the next 50 samples as long as the rate continues to be outside the 20% tolerance. Once 50 samples are collected the new frame rate is updated and the filter cutoffs are adjusted. Only filters set with their cutoffs = 0 (auto) will be adjusted. There is a 2 second guard time after a successful update before retraining can start again to prevent rapid switching back and forth.
The logic is optimized to not perform any training if the filters are set to manual cutoffs. So there is an opportunity for advanced users to choose specific cutoffs and reduce the PID loop load slightly. However this is not recommended for Crossfire or other protocols that might change their rx frame rate.
Updated the output of the `rc_smoothing_info` cli command to match the revised logic.
