gh-118608: datetime: Fix use-after-free on embedded CPython

[neonene]

Debug build on Windows (and CI: 7bbce38):

>_testembed_d test_repeated_init_exec "import datetime" --- Loop #1 --- --- Loop #2 --- Assertion failed: PyUnicode_CheckExact(ep_key), file C:\a\Objects\dictobject.c, line 1119 

At the Loop #2, the static types are carried over in the _datetime module, but their tp_dict no longer has valid keys, since all interned strings (keys) are freed after _PyUnicode_ClearInterned() in unicodeobject.c is invoked.

To check a key without a crash, the following strings need to be statically allocated:

• The names in PyMemberDef array
• The names in PyMethodDef array
• The names in PyGetSetDef array
• The key parameters of the PyDict_SetItemString(tp_dict, key, value) calls.

This patch includes the names that are already statically allocated (e.g. getset names).

• Issue: Memory leak on executables embedded with 3.13 #113055

• Issue: Initialize/Finalize Python multiple time and import datetime each time lead to a memory corruption #118608