net/dumbpipe: New port: Unix pipes between devices

Dumbpipe is inspired by the unix tool netcat. While netcat works with IP
addresses, dumbpipe works with 256 bit node ids and therefore is
somewhat location transparent. In addition, connections are encrypted
using TLS. Iroh-net will take case of hole punching and NAT traversal
whenever possible, and fall back to a relay if hole punching does not
succeed.