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
diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index 24b1188..355bf10 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -28,7 +28,7 @@
 #include "mbedtls/ecdsa.h"
 #endif
 
-#if defined(MBEDTLS_USE_PSA_CRYPTO) || defined(MBEDTLS_PSA_CRYPTO_C)
+#if defined(MBEDTLS_PSA_CRYPTO_C)
 #include "psa/crypto.h"
 #endif
 
@@ -615,7 +615,6 @@
                     unsigned char *sig, size_t sig_size, size_t *sig_len,
                     int (*f_rng)(void *, unsigned char *, size_t), void *p_rng);
 
-#if defined(MBEDTLS_PSA_CRYPTO_C)
 /**
  * \brief           Make signature given a signature type.
  *
@@ -652,7 +651,6 @@
                         unsigned char *sig, size_t sig_size, size_t *sig_len,
                         int (*f_rng)(void *, unsigned char *, size_t),
                         void *p_rng);
-#endif /* MBEDTLS_PSA_CRYPTO_C */
 
 /**
  * \brief           Restartable version of \c mbedtls_pk_sign()