Kconfig and MicroPython config is not updated yet.
* start to refactor lv_conf.h
* further mem refactoring
* create lv_mem_builtin.c/h
* update lv_conf_internal.h
* add lv_strlen and lv_strncpy
* rename LV_DRAW_COMPLEX to LV_USE_DRAW_MASK
* update lv_conf_template
* minor fix