Add Arduino framework support for ESP32-C6 boards

[mertdemirel95]

Arduino-ESP32 core (v3.x) officially supports ESP32-C6 devices and ESP32-C6 boards compile and run successfully with Arduino framework
in Arduino IDE.

However, PlatformIO ESP32-C6 board definitions do not list "arduino" as a supported framework, resulting in the error: "This board doesn't support arduino framework!"

Request:
Please enable Arduino framework support for ESP32-C6 boards (e.g. esp32-c6-devkitc-1) by adding Arduino to the supported frameworks in the board manifest files.

This would align PlatformIO with the current Arduino-ESP32 support and allow existing Arduino projects to migrate to ESP32-C6.

[Jason2866]

See #1225 so C6 is not supported with the Arduino version used from Platformio.