Rename generator functions to psa_key_derivation_xxx

Generators are mostly about key derivation (currently: only about key
derivation). "Generator" is not a commonly used term in cryptography.
So favor "derivation" as terminology. Call a generator a key
derivation operation structure, since it behaves like other multipart
operation structures. Furthermore, the function names are not fully
consistent.

In this commit, I rename the functions to consistently have the prefix
"psa_key_derivation_". I used the following command:

    perl -i -pe '%t = (
        psa_crypto_generator_t => "psa_key_derivation_operation_t",
        psa_crypto_generator_init => "psa_key_derivation_init",
        psa_key_derivation_setup => "psa_key_derivation_setup",
        psa_key_derivation_input_key => "psa_key_derivation_input_key",
        psa_key_derivation_input_bytes => "psa_key_derivation_input_bytes",
        psa_key_agreement => "psa_key_derivation_key_agreement",
        psa_set_generator_capacity => "psa_key_derivation_set_capacity",
        psa_get_generator_capacity => "psa_key_derivation_get_capacity",
        psa_generator_read => "psa_key_derivation_output_bytes",
        psa_generate_derived_key => "psa_key_derivation_output_key",
        psa_generator_abort => "psa_key_derivation_abort",
        PSA_CRYPTO_GENERATOR_INIT => "PSA_KEY_DERIVATION_OPERATION_INIT",
        PSA_GENERATOR_UNBRIDLED_CAPACITY => "PSA_KEY_DERIVATION_UNLIMITED_CAPACITY",
        ); s/\b(@{[join("|", keys %t)]})\b/$t{$1}/ge' $(git ls-files)
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 2681442..42d8230 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -526,7 +526,7 @@
     psa_algorithm_t alg;
     psa_key_policy_t policy;
     psa_key_handle_t master_slot;
-    psa_crypto_generator_t generator = PSA_CRYPTO_GENERATOR_INIT;
+    psa_key_derivation_operation_t generator = PSA_KEY_DERIVATION_OPERATION_INIT;
 
     if( ( status = psa_allocate_key( &master_slot ) ) != PSA_SUCCESS )
         return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
@@ -556,20 +556,20 @@
                                  dlen );
     if( status != PSA_SUCCESS )
     {
-        psa_generator_abort( &generator );
+        psa_key_derivation_abort( &generator );
         psa_destroy_key( master_slot );
         return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
     }
 
-    status = psa_generator_read( &generator, dstbuf, dlen );
+    status = psa_key_derivation_output_bytes( &generator, dstbuf, dlen );
     if( status != PSA_SUCCESS )
     {
-        psa_generator_abort( &generator );
+        psa_key_derivation_abort( &generator );
         psa_destroy_key( master_slot );
         return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
     }
 
-    status = psa_generator_abort( &generator );
+    status = psa_key_derivation_abort( &generator );
     if( status != PSA_SUCCESS )
     {
         psa_destroy_key( master_slot );
@@ -892,7 +892,7 @@
             /* Perform PSK-to-MS expansion in a single step. */
             psa_status_t status;
             psa_algorithm_t alg;
-            psa_crypto_generator_t generator = PSA_CRYPTO_GENERATOR_INIT;
+            psa_key_derivation_operation_t generator = PSA_KEY_DERIVATION_OPERATION_INIT;
             psa_key_handle_t psk;
 
             MBEDTLS_SSL_DEBUG_MSG( 2, ( "perform PSA-based PSK-to-MS expansion" ) );
@@ -913,19 +913,19 @@
                                          master_secret_len );
             if( status != PSA_SUCCESS )
             {
-                psa_generator_abort( &generator );
+                psa_key_derivation_abort( &generator );
                 return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
             }
 
-            status = psa_generator_read( &generator, session->master,
+            status = psa_key_derivation_output_bytes( &generator, session->master,
                                          master_secret_len );
             if( status != PSA_SUCCESS )
             {
-                psa_generator_abort( &generator );
+                psa_key_derivation_abort( &generator );
                 return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
             }
 
-            status = psa_generator_abort( &generator );
+            status = psa_key_derivation_abort( &generator );
             if( status != PSA_SUCCESS )
                 return( MBEDTLS_ERR_SSL_HW_ACCEL_FAILED );
         }