move esp8266 board to PlatformIO CI

Arduino CLI seems to have trouble getting the esp8266 core that
corresponds to the fqbn prefix esp8266com:esp8266

.github/workflows/build_arduino.yml

@@ -98,7 +98,6 @@ jobs:
           - "arduino:megaavr:uno2018"
           # - "arduino:megaavr:nano4809"  # board not found
           - "arduino:sam:arduino_due_x_dbg"
-          - "esp8266com:esp8266:nodemcuv2"
           - "espressif:esp32:adafruit_qtpy_esp32s2"
 
         # By default, don't generate size deltas data.
@@ -150,8 +149,6 @@ jobs:
             - name: arduino:sam
             - name: arduino:samd
             - name: arduino:mbed
-            - name: esp8266com:esp8266
-              source-url: https://arduino.esp8266.com/stable/package_esp8266com_index.json
             - name: espressif:esp32
               source-url: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
       

.github/workflows/build_platformIO.yml

@@ -114,6 +114,7 @@ jobs:
           - "teensylc"
           - "genericSTM32F411CE"
           - "blackpill_f103c8"
+          - "nodemcuv2"
 
     steps:
     - uses: actions/checkout@v2