gh-123446: Fix empty function names in TypeErrors in _csv module

[sobolevn]

After:

>>> import _csv
>>> _csv.reader()
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    _csv.reader()
    ~~~~~~~~~~~^^
TypeError: _csv.reader expected at least 1 argument, got 0
>>> _csv.writer()
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    _csv.writer()
    ~~~~~~~~~~~^^
TypeError: _csv.writer expected at least 1 argument, got 0
>>> _csv.register_dialect()
Traceback (most recent call last):
  File "<python-input-3>", line 1, in <module>
    _csv.register_dialect()
    ~~~~~~~~~~~~~~~~~~~~~^^
TypeError: _csv.register_dialect expected at least 1 argument, got 0

Questions:

1. Do I need to test this? Seems minor enough
2. _csv. or csv.? Technically the module is _csv, but users can see this when these names are re-exported in csv module. I prefer to show the real name.

CC @hauntsaninja, because you have several recent commits to this module.
CC @serhiy-storchaka, because you commented on the issue.

• Issue: PyArg_UnpackTuple is used with name="" #123446

[serhiy-storchaka]

This unnecessary exposes the implementation detail (the private module name).

>>> import csv
>>> csv.reader
<built-in function reader>
>>> csv.reader()
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    csv.reader()
    ~~~~~~~~~~^^
TypeError: _csv.reader expected at least 1 argument, got 0

Compare with:

>>> import os
>>> os.mkdir()
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    os.mkdir()
    ~~~~~~~~^^
TypeError: mkdir() missing required argument 'path' (pos 1)

[sobolevn]

Yes, this was my open question. I will remove the module name.

@hauntsaninja sorry, I should have made this more clear :(