gh-85432: Harmonise parameter names between C and pure-Python implementations of datetime.time.strftime, datetime.datetime.fromtimestamp - #99993

>>> import time, datetime
>>> datetime.time().strftime(format="%f")
'000000'
>>> datetime.datetime.fromtimestamp(timestamp=time.time())
datetime.datetime(2022, 12, 4, 16, 23, 25, 69430)
>>> exit()

>>> import sys
>>> sys.modules["_datetime"] = None
>>> import time, datetime
>>> datetime.time().strftime(format="%f")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: time.strftime() got an unexpected keyword argument 'format'
>>> datetime.datetime.fromtimestamp(timestamp=time.time())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: datetime.fromtimestamp() got an unexpected keyword argument 'timestamp'