Inconsistent `Image.open(str)`

[senyai]

Image.open("") must raise an exception matching open("")

In [1]: from PIL import Image

In [2]: Image.open("non_existent_file")
---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
Cell In[2], line 1
----> 1 Image.open("non_existent_file")

File ~/.local/lib/python3.13/site-packages/PIL/Image.py:3505, in open(fp, mode, formats)
   3502     filename = os.fspath(fp)
   3504 if filename:
-> 3505     fp = builtins.open(filename, "rb")
   3506     exclusive_fp = True
   3507 else:

FileNotFoundError: [Errno 2] No such file or directory: 'non_existent_file'

In [3]: Image.open("")
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
File ~/.local/lib/python3.13/site-packages/PIL/Image.py:3511, in open(fp, mode, formats)
   3510 try:
-> 3511     fp.seek(0)
   3512 except (AttributeError, io.UnsupportedOperation):

AttributeError: 'str' object has no attribute 'seek'

During handling of the above exception, another exception occurred:

AttributeError                            Traceback (most recent call last)
Cell In[3], line 1
----> 1 Image.open("")

File ~/.local/lib/python3.13/site-packages/PIL/Image.py:3513, in open(fp, mode, formats)
   3511     fp.seek(0)
   3512 except (AttributeError, io.UnsupportedOperation):
-> 3513     fp = io.BytesIO(fp.read())
   3514     exclusive_fp = True
   3516 prefix = fp.read(16)

AttributeError: 'str' object has no attribute 'read'

[radarhere]

I've created #9048 to resolve this.