Fix usb_cdc.enable(console=False, data=True)

[dhalbert]

usb_cdc.enable(console=False, data=True) was not working.

• Set usb_cdc defaults correctly
• Use correct TinyUSB itf values when only one CDC is used. Number them from zero. This was the main bug.
• Don't watch for ctrl-c if console is not enabled.
• add board.LED to Metro M4. (Discovered it was missing by accident when i was trying to blink the led for debugging purposes).'

Tested on Feather STM32F405 and on Metro M4.

Thanks to discord user osten (@pdecherf) who found the problem and tested the fix on an STM32F405.

[jepler]

Makes sense, but no testing performed. Are there more places we should switch to tud_cdc_n, in the long term?

[dhalbert]

Makes sense, but no testing performed. Are there more places we should switch to tud_cdc_n, in the long term?

I looked in all the places to understand them, and added comments. Mainly, I fixed the broken simmel build.

[jepler]

thanks! once again, no testing performed.