gh-89979: Sync C/Python datetime implementations positional arguments

[StanFromIreland]

My tasklist

• tzinfo.tzname
• tzinfo.utcoffset
• tzinfo.dst
• tzinfo.fromutc
• date.fromordinal
• date.fromisoformat
• date.format
• date.le
• date.lt
• date.ge
• date.gt
• date.add
• date.radd
• date.sub
• date.reduce_ex Removed
• time.le
• time.lt
• time.ge
• time.gt
• time.fromisoformat
• time.format
• timedelta.add
• timedelta.radd
• timedelta.sub
• timedelta.rsub
• timedelta.mul
• timedelta.rmul
• timedelta.floordiv
• timedelta.truediv
• timedelta.mod
• timedelta.divmod
• timedelta.le
• timedelta.lt
• timedelta.ge
• timedelta.gt
• datetime.utcfromtimestamp
• datetime.fromisoformat
• datetime.strptime
• datetime.le
• datetime.lt
• datetime.ge
• datetime.gt

• Issue: Many method parameters in the datetime module are positional-only in the C implementation but positional-or-keyword in the Python implementation #89979

[serhiy-storchaka]

I'll review this PR after adding more signatures in the C implementation. See #136573.