* GPIO refactoring
GPIO now using ESP-IDF API on all chips.
LEDC interrupt fix removed - no longer needed.
Edited pins_arduino.h in variants according to changes in gpio.
* Edited analog channels functions
M5Stack variant (pins_arduino.h) file is not automatically included,
because boards.txt m5stack-core-esp32.build.variant=esp32
This commit changes m5stack-core-esp32.build.variant from esp32 to m5stack_core_esp32
also rename M5Stack variant directory from m5stack-core-esp32 to m5stack_core_esp32
