linux/lwip: Wrap some IO posix functions
* to workaourd the FreeRTOS EINTR issue (when building without lwip)
* to correctly choose the sub-system based on fd (when building with
lwip) -- passing control to either linux/system or to lwip
This commit also addapts tapio-if to provide DHCP client by default and
configurable settings for static IP
* Added a POSIX/Linux simulator that is compatible with the Amazon
FreeRTOS SMP API. Note that the simulator itself is still
single core, like the IDF FreeRTOS POSIX/Linux simulator.