Add support for ESP32-C6

[HenningHolmDE]

This adds support for ESP32-C6 by bumping the ESP-IDF version to v5.1 and providing the required MCU environment variable. Also, this fixes the compilation on Rust 1.74 by bumping the ESP-IDF Rust dependencies (fixes #3).

Unfortunately, I can only test this on ESP32-C3 and ESP32-C6 hardware, but at least building for the Xtensa targets still works on my machine.