gh-106320: Remove private _PyEval function (#108433)

Move private _PyEval functions to the internal C API
(pycore_ceval.h):

* _PyEval_GetBuiltin()
* _PyEval_GetBuiltinId()
* _PyEval_GetSwitchInterval()
* _PyEval_MakePendingCalls()
* _PyEval_SetProfile()
* _PyEval_SetSwitchInterval()
* _PyEval_SetTrace()

No longer export most of these functions.

Objects/iterobject.c

@@ -3,6 +3,7 @@
 #include "Python.h"
 #include "pycore_abstract.h"      // _PyObject_HasLen()
 #include "pycore_call.h"          // _PyObject_CallNoArgs()
+#include "pycore_ceval.h"         // _PyEval_GetBuiltin()
 #include "pycore_object.h"        // _PyObject_GC_TRACK()
 
 typedef struct {