All credits to RicardoGA

Additional follow-up the PR #3631(Encapsulate Stepper, Planner, Endstops in singleton classes)

・Change from abort_on_endstop_hit to stepper.abort_on_endstop_hit in endstop.cpp, Marlin_main.cpp, and ultralcd.cpp
・Add include path to cardreader.h and temperature.h in endstop.cpp(for CardReader class and disable_all_heaters())
It fix compilation error when ABORT_ON_ENDSTOP_HIT_FEATURE_ENABLED and SDSUPPORT are enabled.

・Change from digipot_current() to stepper.digipot_current() in Marlin_main.cpp
・Change from digitalPotWrite() to stepper.digitalPotWrite() in Marlin_main.cpp
It fix compilation errors when HAS_DIGIPOTSS is enabled.

・Change from microstep_mode() to stepper.microstep_mode() in Marlin_main.cpp
・Change attribute of microstep_mode() from private to public in stepper.h
・Change from microstep_readings() to stepper.microstep_readings() in Marlin_main.cpp
・Change from microstep_ms() to stepper.microstep_ms() in Marlin_main.
It fix compilation errors when HAS_MICROSTEPS is enabled.