crypto-client: reorganize source files/folders

The goal is to keep psasim as simple as possible:

- do not build a separate lib for psa-ff; build those source
  files as part of server or client
- do not have lot of different makefiles: just 1 that does all
  we need
- do not have several subfolders for headers: only 1 is enough
  for this kind of project

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>

tests/psa-client-server/psasim/include/init.h

@@ -0,0 +1,15 @@
+/* Declarations of internal functions. */
+
+/*
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#include <stdint.h>
+#include <service.h>
+void raise_signal(psa_signal_t signal);
+void __init_psasim(const char **array,
+                   int size,
+                   const int allow_ns_clients_array[32],
+                   const uint32_t versions[32],
+                   const int strict_policy_array[32]);