Websocket address support for Unix Sockets

[ruffsl]

When hosting a foxglove websocket bridge behind a reverse proxy on the same machine, it would be nice to support unix sockets as a host address/port for the websocket server connection. This could be more efficient than redirecting websocket traffic over local loopback network interfaces, with some web servers now natively supporting unix sockets:

• https://caddy.community/t/v2-reverse-proxy-to-unix-socket/7071/5
• https://caddyserver.com/docs/conventions#network-addresses

As a bonus, this could improve the overhead performance/latency in Foxglove Studio as well, if compatible with the Electron app, providing a performative alternative to the deprecated native ROS2 bridge that could've used DDS shared memory transport.

• https://github.com/foxglove/studio/pull/5070

As of writing, it looks like the websocketpp library used here has a ticket and PR implementation for supporting unix sockets:

• Listen on unix socket zaphoyd/websocketpp#557
• Unix-Socket Configuration zaphoyd/websocketpp#1013

[foxhubber]

Internal tracking ticket: FG-3212

[defunctzombie]

@ruffsl Is there a bug you want to report here or is this a feature request? If this is a feature request please post this over in the discussions: https://github.com/orgs/foxglove/discussions rather than this repo as a bug.