Issue #27810: Add _PyCFunction_FastCallKeywords()

Use _PyCFunction_FastCallKeywords() in ceval.c: it allows to remove a lot of
code from ceval.c which was only used to call C functions.
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 508fd82..9de6b83 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2366,7 +2366,7 @@
     return result;
 }
 
-static PyObject *
+PyObject *
 _PyStack_AsDict(PyObject **values, Py_ssize_t nkwargs, PyObject *kwnames,
                 PyObject *func)
 {
@@ -2415,10 +2415,13 @@
     assert((nargs == 0 && nkwargs == 0) || stack != NULL);
 
     if (PyFunction_Check(func)) {
-        /* Fast-path: avoid temporary tuple or dict */
         return _PyFunction_FastCallKeywords(func, stack, nargs, kwnames);
     }
 
+    if (PyCFunction_Check(func)) {
+        return _PyCFunction_FastCallKeywords(func, stack, nargs, kwnames);
+    }
+
     if (nkwargs > 0) {
         kwdict = _PyStack_AsDict(stack + nargs, nkwargs, kwnames, func);
         if (kwdict == NULL) {
diff --git a/Objects/methodobject.c b/Objects/methodobject.c
index 394f1f4..0fe3315 100644
--- a/Objects/methodobject.c
+++ b/Objects/methodobject.c
@@ -155,6 +155,7 @@
     PyObject *result;
     int flags;
 
+    assert(PyCFunction_Check(func));
     assert(func != NULL);
     assert(nargs >= 0);
     assert(nargs == 0 || args != NULL);
@@ -243,6 +244,31 @@
     return result;
 }
 
+PyObject *
+_PyCFunction_FastCallKeywords(PyObject *func, PyObject **stack,
+                              Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *kwdict, *result;
+    Py_ssize_t nkwargs;
+
+    assert(PyCFunction_Check(func));
+
+    nkwargs = (kwnames == NULL) ? 0 : PyTuple_GET_SIZE(kwnames);
+    if (nkwargs > 0) {
+        kwdict = _PyStack_AsDict(stack + nargs, nkwargs, kwnames, func);
+        if (kwdict == NULL) {
+            return NULL;
+        }
+    }
+    else {
+        kwdict = NULL;
+    }
+
+    result = _PyCFunction_FastCallDict(func, stack, nargs, kwdict);
+    Py_XDECREF(kwdict);
+    return result;
+}
+
 /* Methods (the standard built-in methods, that is) */
 
 static void