bpo-31009: Fix support.fd_count() on Windows (#2862)

* bpo-31009: Fix support.fd_count() on Windows

On Windows, test.support.fd_count() now calls
msvcrt.CrtSetReportMode() to not kill the process nor log any error
on stderr on os.dup(fd) if the file descriptor is invalid.

* Fix for release mode
2 files changed