ivory-bsp-stm32: uart driver hit/miss debugging variables have better names
temporary up uart priority to 4
ivory-bsp-stm32: i2c driver has error state for more robustness

- can now detect when missed an rx byte via btf flag, enter an error state
  to terminate transaction and reset peripheral
- these errors happen a whole lot in the px4-all-sensors-test! but not at
  all when the scheduler isn't contested, like in the ms5611-test or
  hmc5883l-test
- still occasionally fails when preempted during rx event handler