[3.13] gh-127257: ssl: Raise OSError for ERR_LIB_SYS (GH-127361)

[miss-islington]

From the ERR_raise manpage:

ERR_LIB_SYS

    This "library code" indicates that a system error is
    being reported.  In this case, the reason code given
    to `ERR_raise()` and `ERR_raise_data()` *must* be
    `errno(3)`.

This PR only handles ERR_LIB_SYS for the high-lever error types
SSL_ERROR_SYSCALL and SSL_ERROR_SSL, i.e., not the ones where
OpenSSL indicates it has some more information about the issue.
(cherry picked from commit f4b31ed)

Co-authored-by: Petr Viktorin [email protected]

• Issue: [tests] test_poplib fails with "env changed" on Arch Linux with OpenSSL 3.4: [SYS] unknown error (_ssl.c:2634) #127257

[encukou]

I'd appreciate a SSL expert opinion on the 3.13 backport -- this is not an obvious bugfix.