[3.13] gh-117398: Convert datetime.IsoCalendarDate To A Heap Type (gh-119637) (gh-119695)

This is the only static type in the module that we will not keep static.

(cherry picked from commit 548a11d5cf1dbb32d86ce0c045130c77f50c1427)
(cherry-picked from commit 34f9b3e7244615d2372614b20e10250e68cc8e61)

Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>
Co-authored by: Kirill Podoprigora <kirill.bast9@mail.ru>