socketpair: support pipe2 where available

socketpair: support pipe2 where available

By replacing pipe with pipe2, it would save us 4 extra system calls of
setting O_NONBLOCK and O_CLOEXEC. This system call is widely supported
across UNIX-like OS's: Linux, *BSD, and SunOS derivatives - Solaris,
illumos, etc.

Ref:
https://man7.org/linux/man-pages/man2/pipe.2.html
https://man.freebsd.org/cgi/man.cgi?query=pipe
https://man.dragonflybsd.org/?command=pipe2
https://man.netbsd.org/pipe.2
https://man.openbsd.org/pipe.2
https://docs.oracle.com/cd/E88353_01/html/E37841/pipe2-2.html
https://illumos.org/man/2/pipe2
https://www.gnu.org/software/gnulib/manual/html_node/pipe2.html

Closes #16987