gh-83994, gh-132843: Fix and improve test_ioctl

[serhiy-storchaka]

• Skip test_ioctl_tcflush if termios.TCFLSH is not available.
• Do not skip ALL ioctl() tests when /dev/tty is not available.

• Issue: test_ioctl skipped -- Unable to open /dev/tty #83994

• Issue: test_ioctl failing on MacOS #132843

[miss-islington-app]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @serhiy-storchaka, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 4b4b9fbb06198f65424ed5be06c59f8b2801b99b 3.13

[bedevere-app]

GH-132850 is a backport of this pull request to the 3.13 branch.

[vstinner]

There are errors on Android on Python 3.13:

• AMD64 Android 3.13: https://buildbot.python.org/#/builders/1592/builds/622
• aarch64 Android 3.13: https://buildbot.python.org/#/builders/1590/builds/641

cc @serhiy-storchaka

ERROR: test_ioctl_signed_unsigned_code_param (test.test_ioctl.IoctlTestsPty.test_ioctl_signed_unsigned_code_param)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.13/test/test_ioctl.py", line 142, in setUp
    self.master_fd, self.slave_fd = pty.openpty()
                                    ~~~~~~~~~~~^^
  File "/data/user/0/org.python.testbed/files/python/lib/python3.13/pty.py", line 34, in openpty
    master_fd, slave_name = _open_terminal()
                            ~~~~~~~~~~~~~~^^
  File "/data/user/0/org.python.testbed/files/python/lib/python3.13/pty.py", line 67, in _open_terminal
    raise OSError('out of pty devices')
OSError: out of pty devices
======================================================================
ERROR: test_ioctl_tcflush (test.test_ioctl.IoctlTestsPty.test_ioctl_tcflush)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/data/user/0/org.python.testbed/files/python/lib/python3.13/test/test_ioctl.py", line 142, in setUp
    self.master_fd, self.slave_fd = pty.openpty()
                                    ~~~~~~~~~~~^^
  File "/data/user/0/org.python.testbed/files/python/lib/python3.13/pty.py", line 34, in openpty
    master_fd, slave_name = _open_terminal()
                            ~~~~~~~~~~~~~~^^
  File "/data/user/0/org.python.testbed/files/python/lib/python3.13/pty.py", line 67, in _open_terminal
    raise OSError('out of pty devices')
OSError: out of pty devices

[serhiy-storchaka]

Should be fixed in #132878.