doc: clarify lifecycle of domain sockets

In UNIX, the domain sockets once created persists until unlinked.
Clarify which ones are persisted and which ones are cleared manually.

In Windows, named pipes are cleared based on reference count,
implemented by the underlying system. Disambiguate this from
Garbage collection of the Node.js runtime.

Refs: https://github.com/nodejs/help/issues/1080

PR-URL: https://github.com/nodejs/node/pull/19471


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>