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.