gh-131798: JIT: Narrow the return type of _CALL_LEN to int (#132940)

Reduce unnecessary guards whenever `len()` is called and used
after.

Co-authored-by: Max Bernstein <tekknolagi@gmail.com>

Python/optimizer_bytecodes.c

@@ -1055,6 +1055,10 @@ dummy_func(void) {
         sym_set_const(callable, (PyObject *)&PyUnicode_Type);
     }
 
+    op(_CALL_LEN, (callable[1], self_or_null[1], args[oparg] -- res)) {
+        res = sym_new_type(ctx, &PyLong_Type);
+    }
+
 // END BYTECODES //
 
 }