gh-111178: fix UBSan failures in Modules/_datetimemodule.c (GH-129774)

Add cast macros for date and time objects

Fix UBSan failures for `PyDateTime_Delta`, `PyDateTime_Date`, `PyDateTime_TZInfo`, `PyDateTime_TimeZone`, `PyDateTime_Time`, `PyDateTime_DateTime`, `PyDateTime_IsoCalendarDate`

Fix up naming

Author: picnixz