Code changes supporting up to 6 extruders

Marlin/src/HAL/HAL_AVR/SanityCheck.h

Marlin/src/HAL/HAL_STM32F7/SanityCheck.h

Marlin/src/Marlin.cpp

Marlin/src/Marlin.h

Marlin/src/core/drivers.h

Marlin/src/core/language.h

Marlin/src/feature/I2CPositionEncoder.cpp

Marlin/src/feature/controllerfan.cpp

Marlin/src/feature/power.cpp

Marlin/src/feature/runout.cpp

Marlin/src/feature/runout.h

Marlin/src/feature/solenoid.cpp

Marlin/src/feature/tmc_util.cpp

Marlin/src/feature/tmc_util.h

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

Marlin/src/gcode/feature/trinamic/M906.cpp

Marlin/src/gcode/feature/trinamic/M911-M915.cpp

Marlin/src/inc/Conditionals_post.h

Marlin/src/inc/SanityCheck.h

Marlin/src/lcd/language/language_an.h