Make PyXXX_Fini() functions private (GH-15531)

For example, rename PyTuple_Fini() to _PyTuple_Fini().

These functions are only declared in the internal C API.

Objects/bytesobject.c

@@ -3047,7 +3047,7 @@ error:
 }
 
 void
-PyBytes_Fini(void)
+_PyBytes_Fini(void)
 {
     int i;
     for (i = 0; i < UCHAR_MAX + 1; i++)

Objects/classobject.c

@@ -375,7 +375,7 @@ PyMethod_ClearFreeList(void)
 }
 
 void
-PyMethod_Fini(void)
+_PyMethod_Fini(void)
 {
     (void)PyMethod_ClearFreeList();
 }

Objects/dictobject.c

@@ -282,7 +282,7 @@ _PyDict_DebugMallocStats(FILE *out)
 
 
 void
-PyDict_Fini(void)
+_PyDict_Fini(void)
 {
     PyDict_ClearFreeList();
 }

Objects/floatobject.c

@@ -2031,7 +2031,7 @@ PyFloat_ClearFreeList(void)
 }
 
 void
-PyFloat_Fini(void)
+_PyFloat_Fini(void)
 {
     (void)PyFloat_ClearFreeList();
 }

Objects/frameobject.c

@@ -997,7 +997,7 @@ PyFrame_ClearFreeList(void)
 }
 
 void
-PyFrame_Fini(void)
+_PyFrame_Fini(void)
 {
     (void)PyFrame_ClearFreeList();
 }

Objects/genobject.c

@@ -1463,7 +1463,7 @@ PyAsyncGen_ClearFreeLists(void)
 }
 
 void
-PyAsyncGen_Fini(void)
+_PyAsyncGen_Fini(void)
 {
     PyAsyncGen_ClearFreeLists();
 }

Objects/listobject.c

@@ -138,7 +138,7 @@ PyList_ClearFreeList(void)
 }
 
 void
-PyList_Fini(void)
+_PyList_Fini(void)
 {
     PyList_ClearFreeList();
 }

Objects/longobject.c

@@ -5869,7 +5869,7 @@ _PyLong_Init(void)
 }
 
 void
-PyLong_Fini(void)
+_PyLong_Fini(void)
 {
     /* Integers are currently statically allocated. Py_DECREF is not
        needed, but Python must forget about the reference or multiple

Objects/methodobject.c

@@ -319,7 +319,7 @@ PyCFunction_ClearFreeList(void)
 }
 
 void
-PyCFunction_Fini(void)
+_PyCFunction_Fini(void)
 {
     (void)PyCFunction_ClearFreeList();
 }

Objects/setobject.c

@@ -2318,7 +2318,7 @@ PySet_ClearFreeList(void)
 }
 
 void
-PySet_Fini(void)
+_PySet_Fini(void)
 {
     Py_CLEAR(emptyfrozenset);
 }

Objects/sliceobject.c

@@ -100,7 +100,8 @@ PyObject _Py_EllipsisObject = {
  * created and then deleted again
  */
 static PySliceObject *slice_cache = NULL;
-void PySlice_Fini(void)
+
+void _PySlice_Fini(void)
 {
     PySliceObject *obj = slice_cache;
     if (obj != NULL) {

Objects/tupleobject.c

@@ -989,7 +989,7 @@ PyTuple_ClearFreeList(void)
 }
 
 void
-PyTuple_Fini(void)
+_PyTuple_Fini(void)
 {
 #if PyTuple_MAXSAVESIZE > 0
     /* empty tuples are used all over the place and applications may