- Addressing #3689, et. al.

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.

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

plan_bed_level_matrix -> planner.bed_level_matrix in multi extruders section of Marlin_main.cpp
It probably fix the Issue #3658(plan_bed_level_matrix not declarate).

movesplanned() -> planner.movesplanned() in ADVANCED_OK section of Marlin_main.cpp
It fix compilation error when ADVANCED_OK is enabled

The fix is simple. Most changes are because of changed indendation,
bacause of leaving early for wrong tool number

- Use new `DEBUG_POS` macro for `DELTA` debug
- Neaten up `prepare_move` a smidgen
- Remove an old commented `prepare_move()` line

This G-code is asynchronously handled in the get_serial_commands() parser.

Signed-off-by: Jeff K

As noted by @snowzach in #3461