Issue #18874: _PyObject_Malloc/Realloc/Free() now falls back on

_PyMem_RawMalloc/Realloc/Free, instead of _PyMem_Malloc/Realloc/Free.  So it
becomes possible to use the fast pymalloc allocator for the PYMEM_DOMAIN_MEM
domain (PyMem_Malloc/Realloc/Free functions).