dut monitor: Support local port forwarding option

[mhiramat]

Add the options for local port forwarding for each DUT on cro3 dut monitor. This allows user to make DUT working as gateway. e.g.

cro3 dut monitor mydut,192.168.111.222:3456

This will map some local port to 192.168.111.222:3456 via mydut.