Implement psa_generate_key_custom

Implement `psa_generate_key_custom()` and
`psa_key_derivation_output_key_custom()`. These functions replace
`psa_generate_key_ext()` and `psa_key_derivation_output_key_ext()`.
They have the same functionality, but a slightly different interface:
the `ext` functions use a structure with a flexible array member to pass
variable-length data, while the `custom` functions use a separate parameter.

Keep the `ext` functions for backward compatibility with Mbed TLS 3.6.0.
But make them a thin wrapper around the new `custom` functions.

Duplicate the test code and data. The test cases have to be duplicated
anyway, and the test functions are individually more readable this way.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_crypto_rsa.c b/library/psa_crypto_rsa.c
index 2f613b3..f8e36d8 100644
--- a/library/psa_crypto_rsa.c
+++ b/library/psa_crypto_rsa.c
@@ -241,7 +241,7 @@
 
 psa_status_t mbedtls_psa_rsa_generate_key(
     const psa_key_attributes_t *attributes,
-    const psa_key_production_parameters_t *params, size_t params_data_length,
+    const uint8_t *custom_data, size_t custom_data_length,
     uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length)
 {
     psa_status_t status;
@@ -249,8 +249,8 @@
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     int exponent = 65537;
 
-    if (params_data_length != 0) {
-        status = psa_rsa_read_exponent(params->data, params_data_length,
+    if (custom_data_length != 0) {
+        status = psa_rsa_read_exponent(custom_data, custom_data_length,
                                        &exponent);
         if (status != PSA_SUCCESS) {
             return status;