Expand on serial debugging (#13577)

Marlin/src/core/debug_out.h

Marlin/src/core/serial.cpp

Marlin/src/core/serial.h

Marlin/src/feature/I2CPositionEncoder.cpp

Marlin/src/feature/I2CPositionEncoder.h

Marlin/src/feature/bedlevel/bedlevel.cpp

Marlin/src/feature/bedlevel/bedlevel.h

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

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/power_loss_recovery.cpp

Marlin/src/feature/power_loss_recovery.h

Marlin/src/feature/tmc_util.cpp

Marlin/src/feature/tmc_util.h

Marlin/src/gcode/bedlevel/G26.cpp

Marlin/src/gcode/bedlevel/ubl/M49.cpp

Marlin/src/gcode/feature/powerloss/M1000.cpp

Marlin/src/gcode/gcode.cpp

Marlin/src/gcode/gcode.h