Up/down arrows do not process over UART

[mcknly]

The up/down arrows do not work to trigger the command history feature when using CLI over UART, however they do work with CLI over USB. It is believed that is because more bytes are buffered over USB, whereas with UART only a single byte is buffered/services at a time. This means that if multiple bytes are sent in series and the CLI task does not service them fast enough, they will be dropped. Up/down arrows use escape codes that are 3 bytes long, so instead of receiving \033[A (or ESC followed by ASCII [A) for example up arrow, the CLI will only receive and echo back the last byte A.

It may be possible to fix this with changes to RTOS task scheduling, otherwise may need to implement a multi-byte buffer for the CLI UART.