[eppp]: Add wifi-connectivity example

[david-cermak]

Warning this is very WIP

             SLAVE micro                                  HOST micro
    \|/  +------------------+                           +------------------+
     |   | PRC   TLS-server |                           | TLS-client       |
     |   |    custom channel|                           | wifi_remote API  |
     +---+ WiFi       PPPoS |======== UART / SPI =======| PPPoS client     |
         |          (server)|                           |                  |
         +------------------+                           +------------------+

Throughput @SPI

• TCP ~ 11 Mbps both ways
• UDP ~ 15 Mpbs