vere: adds %quic loom measurement, support it and |mass in conn

[joemfb]

Resolves #

[joemfb]

These changes should be ready to go. I've cleaned up crash issues with the async-request lifecycle, and refactored some of the interfaces from #675.

To work around the absence of -W on macos nc, I've used socat -t300 -,ignoreeof UNIX-CONNECT:$SHIP/.urb/conn.sock.

The build issues here are a little strange. I think that dependencies are not properly declared between packages in the zig build system. I had local build issues adding new motes and using them in serf.c -- I ended up manually removing the zig cache.

[joemfb]

At some point, conn.c should be decoupled from newt.c so that these socket shenanigans are no longer necessary. Errors / EOF on the read side of a conn connection should not (necessarily) tear down the entire connection.