bpo-40428: Remove PyTuple_ClearFreeList() function (GH-19769)

Remove the following function from the C API:

* PyAsyncGen_ClearFreeLists()
* PyContext_ClearFreeList()
* PyDict_ClearFreeList()
* PyFloat_ClearFreeList()
* PyFrame_ClearFreeList()
* PyList_ClearFreeList()
* PySet_ClearFreeList()
* PyTuple_ClearFreeList()

Make these functions private, move them to the internal C API and
change their return type to void.

Call explicitly PyGC_Collect() to free all free lists.

Note: PySet_ClearFreeList() did nothing.
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 04f968e..faa02f2 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -1998,25 +1998,22 @@
     return 1;
 }
 
-int
-PyFloat_ClearFreeList(void)
+void
+_PyFloat_ClearFreeList(void)
 {
     PyFloatObject *f = free_list, *next;
-    int i = numfree;
-    while (f) {
+    for (; f; f = next) {
         next = (PyFloatObject*) Py_TYPE(f);
         PyObject_FREE(f);
-        f = next;
     }
     free_list = NULL;
     numfree = 0;
-    return i;
 }
 
 void
 _PyFloat_Fini(void)
 {
-    (void)PyFloat_ClearFreeList();
+    _PyFloat_ClearFreeList();
 }
 
 /* Print summary info about the state of the optimized allocator */