Clean up HAL ADC, old test scripts

Marlin/src/HAL/HAL_AVR/HAL.h

Marlin/src/HAL/HAL_DUE/HAL.cpp

Marlin/src/HAL/HAL_DUE/HAL.h

Marlin/src/HAL/HAL_ESP32/HAL.cpp

Marlin/src/HAL/HAL_ESP32/HAL.h

Marlin/src/HAL/HAL_LINUX/HAL.cpp

Marlin/src/HAL/HAL_LINUX/HAL.h

Marlin/src/HAL/HAL_SAMD51/HAL.cpp

Marlin/src/HAL/HAL_SAMD51/HAL.h

Marlin/src/HAL/HAL_TEENSY35_36/HAL.cpp

buildroot/bin/backup_ramps

buildroot/bin/build_marlin

buildroot/bin/build_marlin_fail

buildroot/bin/build_marlin_pio

buildroot/bin/build_marlin_teensy35

buildroot/bin/env_backup

buildroot/bin/env_clean

buildroot/bin/env_restore

buildroot/bin/restore_configs

buildroot/bin/update_defaults