GitLab

Add a new board type for ESP32-C3 revision 3 and up that implement the USB
serial/JTAG port on pin 18 and 19.  This variant uses the USB serial for
programming and console, leaving the UART free.

- Pins 18 and 19 are correctly reserved for this variant.  Also pins 14-17
  are reserved for flash for any ESP32-C3 so they can't be reconfigured
  anymore to crash the system.
- Added usb_serial_jtag.c and .h to implement this interface.
- Interface was tested to work correctly together with webrepl.
- Interface was tested to work correctly when sending and receiving
  large files with ampy.
- Disconnecting terminal or USB will not hang the system when it's
  trying to print.