Tracking issue for Unix Sockets in the standard library

[alexcrichton]

Tracking issue for rust-lang/rfcs#1479

Implemented in #32302, so I'm gonna go ahead and tag this as B-unstable. Now just needs to go through FCP!

[alexcrichton]

🔔 This issue is now entering its cycle-long final comment period for stabilization 🔔

The libs team discussed this and the conclusion was that these APIs have been quite battle-tested in the unix-socket crate so although they may not have gotten much use from the standard library we're pretty confident in their APIs.

[alexcrichton]

The libs team discussed during triage and the decision was to stabilize