Remove esp8266 support in favor of ESP8266 RTOS SDK

.gitlab-ci.yml

include/arch/esp8266/driver/counter.h

include/arch/esp8266/driver/gpio.h

include/arch/esp8266/driver/stdin.h

include/arch/esp8266/driver/stdout.h

include/arch/esp8266/driver/uptime.h

include/arch/esp8266/user_config.h

script/mkconfig

src/arch/esp8266/Kconfig

src/arch/esp8266/Makefile.inc

src/arch/esp8266/arch.cc

src/arch/esp8266/driver/counter.cc

src/arch/esp8266/driver/gpio.cc

src/arch/esp8266/driver/stdin.cc

src/arch/esp8266/driver/stdout.cc

src/arch/esp8266/driver/uptime.cc

src/arch/esp8266/prompt

src/driver/Kconfig

src/driver/ccs811.cc

src/driver/soft_i2c.cc