USB CDC sends corrupted data in specifc circumstances

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In uart_task.c we use tud_cdc_n_read to read from the USB_CDC_ESP32. This function returns a length and places data into a buffer.

When connecting a terminal program (tested with screen) the tud_cdc_n_read returns garbage data, specifically some data that has previously been sent by the ESP32 to the RP2040, so it's data that was in the transmit buffer of the CDC interface. The tud_cdc_n_read actively writes to our buffer so this appears to be an SDK bug.

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Relates to badgeteam/badgePython#25 as this garbage data is what is causing the ESP32 to crash (though the ESP32 should never crash when receiving garbage data, so there is another bug to be solved over at the ESP32 side).