[3.7] gh-97612: Fix shell injection in get-remote-certificate.py (#97613)

[vstinner]

Fix a shell code injection vulnerability in the
get-remote-certificate.py example script. The script no longer uses a shell to run "openssl" commands. Issue reported and initial fix by Caleb Shortt.

Remove the Windows code path to send "quit" on stdin to the "openssl s_client" command: use DEVNULL on all platforms instead.

Co-authored-by: Caleb Shortt [email protected]
(cherry picked from commit 83a0f44)

• Issue: [security] Tools/scripts/get-remote-certificate.py is vulnerable to shell code injection #97612

[vstinner]

Unrelated to this PR: test_int fails randomly on Windows x64:

FAIL: test_denial_of_service_prevented_str_to_int (test.test_int.IntSubclassStrDigitLimitsTests)
Regression test: ensure we fail before performing O(N**2) work.
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Traceback (most recent call last):
  File "D:\a\cpython\cpython\lib\test\test_int.py", line 654, in test_denial_of_service_prevented_str_to_int
    self.assertLess(seconds_to_fail_extra_huge, seconds_to_convert/8)
AssertionError: 0.015625 not less than 0.013671875

I re-run the job.