psa: Use application key ID where necessary

Avoid compiler errors when MBEDTLS_PSA_CRYPTO_KEY_FILE_ID_ENCODES_OWNER
is set by using the application ID type.

    [Error] psa_crypto_slot_management.c@175,9: used type 'psa_key_id_t' (aka 'psa_key_file_id_t') where arithmetic or pointer type is required
diff --git a/include/psa/crypto_extra.h b/include/psa/crypto_extra.h
index 62d7b82..6293e3e 100644
--- a/include/psa/crypto_extra.h
+++ b/include/psa/crypto_extra.h
@@ -251,9 +251,9 @@
     /** Number of slots that are not used for anything. */
     size_t empty_slots;
     /** Largest key id value among open keys in internal persistent storage. */
-    psa_key_id_t max_open_internal_key_id;
+    psa_app_key_id_t max_open_internal_key_id;
     /** Largest key id value among open keys in secure elements. */
-    psa_key_id_t max_open_external_key_id;
+    psa_app_key_id_t max_open_external_key_id;
 } mbedtls_psa_stats_t;
 
 /** \brief Get statistics about