[Bug]: itertools.count() accepts None for start and step #1251

Describe the bug

itertools.count(None) and itertools.count(0, None) return count(0) on GraalPy. CPython raises TypeError: a number is required, since only an omitted start or step takes the default.

Operating system

macOS

CPU architecture

ARM64

GraalPy version

master a3009f9 (Python 3.13.14); also reproduced on 25.1.3 (Python 3.12.8)

JDK version

No response

Context configuration

No response

Steps to reproduce

import itertools
print(itertools.count(None))
print(itertools.count(0, None))

GraalPy master a3009f9:

count(0)
count(0)

Expected behavior

CPython 3.13.14 (same on 3.12.13), for each call:

TypeError: a number is required

Stack trace

Additional context

The keyword forms count(start=None) and count(step=None) behave the same. A non-number other than None, such as count('a'), already raises the TypeError.

Root Cause

CountBuiltins.CountNode declares start and step with useDefaultForNone = true (CountBuiltins.java#L101-L104), so an explicit None becomes 0 or 1 before the PyNumberCheckNode checks (#L123-L128). CPython's clinic defaults only a missing argument (c_default="NULL"), and itertools_count_impl passes None to PyNumber_Check (itertoolsmodule.c#L4022-L4026).

Fix Suggestion

Drop useDefaultForNone = true from both @ArgumentClinic annotations, so the defaults apply only to an omitted argument.