Only allow supported ESP-IDF targets

[sredman]

Per discussion on #123

Only allow the user to select ESP-IDF targets which support the selected MCU.

This should work without #124, even though some of the MCU targets don't exist until that is merged.

[sredman]

Support matrix here: https://github.com/espressif/esp-idf#esp-idf-release-and-soc-compatibility

[sredman]

Tested end-to-end on my esp32c6 devboard: I can create a fresh project, build, flash, and see "Hello World". I have to edit the targets in the .cargo/config.toml, fix proposed in #124.

[SergioGasquez]

Thanks for your contribution!