Add 'Back' Button for Touch TFT 320x240 (#15060)

Marlin/Configuration.h

Marlin/Configuration_adv.h

Marlin/src/feature/touch/xpt2046.cpp

.../src/lcd/dogm/u8g_dev_tft_320x240_upscale_from_128x64.cpp

Marlin/src/lcd/ultralcd.cpp

Marlin/src/lcd/ultralcd.h

config/default/Configuration.h

config/default/Configuration_adv.h

config/examples/3DFabXYZ/Migbot/Configuration.h

config/examples/3DFabXYZ/Migbot/Configuration_adv.h

config/examples/ADIMLab/Gantry v1/Configuration.h

config/examples/ADIMLab/Gantry v1/Configuration_adv.h

config/examples/ADIMLab/Gantry v2/Configuration.h

config/examples/ADIMLab/Gantry v2/Configuration_adv.h

config/examples/AlephObjects/TAZ4/Configuration.h

config/examples/AlephObjects/TAZ4/Configuration_adv.h

config/examples/Alfawise/U20/Configuration.h

config/examples/Alfawise/U20/Configuration_adv.h

config/examples/AliExpress/CL-260/Configuration.h

config/examples/AliExpress/UM2pExt/Configuration.h