lwIP TCP/IP Network Stack Improvements

This project brings up lwIP on the TI TMS570LC43x under RTEMS. The TMS570 is a high-reliability MCU most recently used as the flight controller on the Ingenuity helicopter. A secondary contribution reintegrates the lwIP stack at the netconn API layer, which eliminates BSD socket indirection, reduces memory footprint, and enables zero-copy tx/rx in RTEMS applications.