[3.13] gh-132124: improve safety nets for creating AF_UNIX socket files (GH-134085...

[3.13] gh-132124: improve safety nets for creating AF_UNIX socket files (GH-134085) (#134448)

* gh-132124: improve safety nets for creating AF_UNIX socket files (GH-134085)

* ensure that we can create AF_UNIX socket files
* emit a warning if system-wide temporary directory is used
(cherry picked from commit 1a07a01014bde23acd2684916ef38dc0cd73c2de)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
* rename warn -> _warn for the 3.13.x backport

* Update Misc/NEWS.d/next/Library/2025-05-16-12-40-37.gh-issue-132124.T_5Odx.rst

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Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>