pk: implement non-PSA mbedtls_pk_sign_ext()

This makes the function always available with its
its implementation depending on MBEDTLS_USE_PSA_CRYPTO.

Related dependencies and tests are updated as well.

Fixes #7583.

Signed-off-by: Tomi Fontanilles <129057597+tomi-font@users.noreply.github.com>
diff --git a/include/mbedtls/config_adjust_legacy_crypto.h b/include/mbedtls/config_adjust_legacy_crypto.h
index e66d67a..74d037d 100644
--- a/include/mbedtls/config_adjust_legacy_crypto.h
+++ b/include/mbedtls/config_adjust_legacy_crypto.h
@@ -235,9 +235,9 @@
 #define MBEDTLS_PSA_CRYPTO_CLIENT
 #endif /* MBEDTLS_PSA_CRYPTO_C */
 
-/* The PK wrappers need pk_write functions to format RSA key objects
- * when they are dispatching to the PSA API. This happens under USE_PSA_CRYPTO,
- * and also even without USE_PSA_CRYPTO for mbedtls_pk_sign_ext(). */
+/* The PK wrappers need pk_write/pk_parse functions to format RSA key objects
+ * when they are dispatching to the PSA API. This happens under MBEDTLS_USE_PSA_CRYPTO,
+ * and even under just MBEDTLS_PSA_CRYPTO_C in psa_crypto_rsa.c. */
 #if defined(MBEDTLS_PSA_CRYPTO_C) && defined(MBEDTLS_RSA_C)
 #define MBEDTLS_PK_C
 #define MBEDTLS_PK_WRITE_C