gh-128074: Support +HH format as time zone for strptime

[donBarbos]

I made the minute (MM) part optional for time zone.

New behavior:

>>> from datetime import datetime
>>> datetime.strptime("2023-05-25T15:35:05.666+11", "%Y-%m-%dT%H:%M:%S.%f%z")
datetime.datetime(2023, 5, 25, 15, 35, 5, 666000, tzinfo=datetime.timezone(datetime.timedelta(seconds=39600)))

Old behavior:

>>> from datetime import datetime
>>> datetime.strptime("2023-05-25T15:35:05.666+11", "%Y-%m-%dT%H:%M:%S.%f%z")
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    datetime.strptime("2023-05-25T15:35:05.666+11", "%Y-%m-%dT%H:%M:%S.%f%z")
    ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../cpython/Lib/_strptime.py", line 700, in _strptime_datetime_datetime
    tt, fraction, gmtoff_fraction = _strptime(data_string, format)
                                    ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File ".../cpython/Lib/_strptime.py", line 453, in _strptime
    raise ValueError("time data %r does not match format %r" %
                     (data_string, format))
ValueError: time data '2023-05-25T15:35:05.666+11' does not match format '%Y-%m-%dT%H:%M:%S.%f%z'

• Issue: datetime.strptime's %z should support +HH #128074

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📚 Documentation preview 📚: https://cpython-previews--130390.org.readthedocs.build/

[StanFromIreland]

This has conflicts now.

[donBarbos]

After adding the %:z directive, I merged the main branch here and changed the regex for %:z so that it could also only read HH format
cc @pganssle I think this PR could be reviewed after adding %:z directive