tests(pki): add security key testing helper functions to torture library

Signed-off-by: Praneeth Sarode <praneethsarode@gmail.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

tests/torture_sk.h

@@ -0,0 +1,40 @@
+/*
+ * torture_sk.h - torture library for testing security keys
+ *
+ * This file is part of the SSH Library
+ *
+ * Copyright (c) 2025 Praneeth Sarode <praneethsarode@gmail.com>
+ *
+ * The SSH Library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ *
+ * The SSH Library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the SSH Library; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#ifndef _TORTURE_SK_H
+#define _TORTURE_SK_H
+
+#include "config.h"
+
+#define LIBSSH_STATIC
+
+#include <stdbool.h>
+
+#include "torture.h"
+#include "torture_pki.h"
+
+void assert_sk_key_valid(ssh_key key,
+                         enum ssh_keytypes_e expected_type,
+                         bool private);
+
+#endif /* _TORTURE_SK_H */