Move datetime-specific code from date methods into datetime class

[5j9]

Simplifies the logic and improves readability by moving datetime-specific code branches to datetime class. Also resolves some code linter warnings about attributes not being defined on date class.

_strftime_p: only raises Exception (AttributeError) on date objects because dates do not have hour attribute.

_strftime_z: only raises AttributeError on a date class becuase date does not have utcoffset attribute.

_strftime_cap_z: date does not have tzname attribute, but datetime has.

[hramezani]

@5j9 please rebase on top of main

[hramezani]

Thanks @5j9

[slashmili]

Nice work @5j9 👍🏼