Use IPv6 localhost when family is 'ipv6

Use IPv6 localhost when family is 'ipv6

This fixes Bug#34193

* src/process.c (Fmake_network_process): Explicitly use ::1 when
using IPv6 with 'local.  Update docstring.

* test/lisp/net/network-stream-tests.el
(make-ipv6-tcp-server-with-unspecified-port):
(make-ipv6-tcp-server-with-specified-port): Test creating ipv6
local server.
(make-server): Add optional family argument, default ipv4
(echo-server-with-local-ipv4): Test connecting to 'local ipv4
(echo-server-with-local-ipv6): Test connecting to 'local ipv6

* doc/lispref/processes.texi (Network Processes): Describe
behavior when using 'local.

* etc/NEWS: Document new 'make-network-process' behavior when
connecting to 'local with ipv6.