Switch key slots to psa_key_attributes_t

Switch `psa_key_slot_t` to the full `psa_key_attributes_t`, now that this
structure only has psa_core_key_attributes_t`.

To minimize the diff without breaking the build much, temporarily make
`psa_key_attributes_t` contain either the `core` field or all the fields.
This allows both things like `slot->attr.core.type` and `slot->attr.type`
to exist. The build breaks with compilers that don't support anonymous
unions and structs, which are only standard C since C11.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_crypto_storage.c b/library/psa_crypto_storage.c
index 13a3c8a..7d1317b 100644
--- a/library/psa_crypto_storage.c
+++ b/library/psa_crypto_storage.c
@@ -235,7 +235,7 @@
 
 void psa_format_key_data_for_storage(const uint8_t *data,
                                      const size_t data_length,
-                                     const psa_core_key_attributes_t *attr,
+                                     const psa_key_attributes_t *attr,
                                      uint8_t *storage_data)
 {
     psa_persistent_key_storage_format *storage_format =
@@ -267,7 +267,7 @@
                                              size_t storage_data_length,
                                              uint8_t **key_data,
                                              size_t *key_data_length,
-                                             psa_core_key_attributes_t *attr)
+                                             psa_key_attributes_t *attr)
 {
     psa_status_t status;
     const psa_persistent_key_storage_format *storage_format =
@@ -314,7 +314,7 @@
     return PSA_SUCCESS;
 }
 
-psa_status_t psa_save_persistent_key(const psa_core_key_attributes_t *attr,
+psa_status_t psa_save_persistent_key(const psa_key_attributes_t *attr,
                                      const uint8_t *data,
                                      const size_t data_length)
 {
@@ -352,7 +352,7 @@
     mbedtls_zeroize_and_free(key_data, key_data_length);
 }
 
-psa_status_t psa_load_persistent_key(psa_core_key_attributes_t *attr,
+psa_status_t psa_load_persistent_key(psa_key_attributes_t *attr,
                                      uint8_t **data,
                                      size_t *data_length)
 {