TMC4671 rewrite + I2C support

This merges all changes regarding TMC4671 improvements and fixes in the meantime.

Changes for TMC:

TMC saves ADC offsets in flash and checks if they are valid
TMC calibration sequence to measure adc offsets and encoder settings
Partial rewrite of encoder alignment routines minimizing movement
Automatic index search and position offset reloading for TMC w. ABN encoders (Autohoming for wheels)
Flux reported in current readout
Experimental external encoder support for tmc (no absolute encoder benefits yet but possible to add)
Faster startup
Allowed combining TMC encoder for commutation and externally in axis selected encoder for gamepad positioning for higher precision in gamepad and better speed for commutation

General changes:

F407 reboots correctly after exiting DFU bootloader (already merged)
Added I2C helper classes and support for PCF8574 button sources
More efficient task activation using notifications instead of semaphores where possible
Fixed hex parsing in commands (xFF equivalent to 255 shortening commands for very long values)
Option to forward SPI encoders to TMC for commutation or combining TMC and axis position sources

Ultrawipf / OpenFFBoard