Clear the following PyTypeObject members of builtin static types in
Py_Finalize():

* tp_bases
* tp_cache
* tp_dict
* tp_mro
* tp_subclasses

Finalize static types initialized by _PyStaticTypes_Init() and
builtin exceptions initialized by _PyExc_Init().

Once a static type is finalized, it must no longer be used.
Use assert(!_PyStaticType_IsFinalized(type)); to ensure that static
type is not finalized.

With this change, Valgrind log:

    possibly lost: 612,326 bytes in 5,503 blocks

becomes:

    possibly lost: 369,346 bytes in 2,805 blocks"

Changes:

* Rename _PyTypes_Init() to _PyStaticTypes_Init().
* Move _PyExc_Fini() call inside finalize_interp_types().