Fake os.open does not handle the O_DIRECTORY flag

[vector-of-bool]

Describe the bug
The POSIX O_DIRECTORY open flag causes open() to mandate that the opened file is a directory. If the file is not a directory, it should fail with ENOTDIR. pyfakefs does not generate such an error, and later attempts to use the resulting fileno as a directory will raise errors.

How To Reproduce

def open_directory(filepath: Path, dirpath: Path):
    filepath.write_text("hey")
    with pytest.raises(NotADirectoryError):
        os.open(filepath, os.O_RDONLY | os.O_DIRECTORY)
    dirpath.mkdir(exist_ok=True)
    with pytest.raises(IsADirectoryError):
        os.open(dirpath, os.O_RDWR | os.O_DIRECTORY)

def test_realfs():
    open_directory(Path("file.txt"), Path("directory.d"))

def test_fakefs(fs):
    open_directory(Path("file.txt"), Path("directory.d"))

Your environment
Please run the following in the environment where the problem happened and
paste the output.

$ python -c "import platform; print(platform.platform())"
Linux-6.7.6-arch1-1-x86_64-with-glibc2.39
$ python -c "import sys; print('Python', sys.version)"
Python 3.11.7 (main, Jan 29 2024, 16:03:57) [GCC 13.2.1 20230801]
$ python -c "from pyfakefs import __version__; print('pyfakefs', __version__)"
pyfakefs 5.4.dev0
$ python -c "import pytest; print('pytest', pytest.__version__)"
pytest 7.2.0