unexpected behavior of tempfile.TemporaryFile() for O_TMPFILE

Bug report

When O_TMPFILE is available:

1. tempfile.TemporaryFile(mode='wb') opens with O_RDWR instead of O_WRONLY, the opener callback ignores mode argument and always use _bin_openflags
2. _bin_openflags has both O_CREAT and O_EXCL set, the opener callback removes O_CREAT from flags but leave O_EXCL, this is an undefined behavior according to Linux open(2) manpage

Your environment

• CPython versions tested on: 3.10
• Operating system and architecture: Linux x86_64

Linked PRs

• gh-133235

先阅读 tempfile.TemporaryFile 及其 opener 回调，重点关注 O_TMPFILE 可用时如何使用 mode 参数和 _bin_openflags。检查 Linux open(2) 对 O_CREAT 和 O_EXCL 的行为，然后验证二进制写入模式使用了预期的访问标志，而不存在未定义的标志组合。