Simpler Allen Key config. Fixes, cleanups from refactor (#15256)

Marlin/src/HAL/HAL_LPC1768/u8g/LCD_I2C_routines.c

Marlin/src/core/macros.h

Marlin/src/core/serial.cpp

Marlin/src/core/serial.h

Marlin/src/feature/I2CPositionEncoder.cpp

Marlin/src/feature/backlash.h

Marlin/src/feature/bedlevel/abl/abl.cpp

Marlin/src/feature/bedlevel/bedlevel.h

Marlin/src/feature/bedlevel/mbl/mesh_bed_leveling.h

Marlin/src/feature/bedlevel/ubl/ubl.h

Marlin/src/feature/bedlevel/ubl/ubl_G29.cpp

Marlin/src/feature/bedlevel/ubl/ubl_motion.cpp

Marlin/src/feature/dac/stepper_dac.cpp

Marlin/src/feature/filwidth.h

Marlin/src/feature/runout.h

Marlin/src/gcode/bedlevel/abl/G29.cpp

Marlin/src/gcode/calibrate/G33.cpp

Marlin/src/gcode/calibrate/G425.cpp

Marlin/src/gcode/calibrate/M425.cpp

Marlin/src/gcode/control/M605.cpp