Switch message cipher consumers to shared media API

tests/test_dm_e2e.c

@@ -262,7 +262,7 @@ static size_t test_body(struct UTUN_INSTANCE* author, uint64_t seq, const char*
     body[32] = 4;
     memcpy(body + 33, "text", 4);
     size_t enc_len = 0;
-    if (dm_encrypt(key, nonce, (const uint8_t*)text, strlen(text), body + 39, &enc_len) != 0) return 0;
+    if (media_ccm_encrypt(key, nonce, (const uint8_t*)text, strlen(text), body + 39, &enc_len) != 0) return 0;
     uint16_t n = (uint16_t)enc_len;
     memcpy(body + 37, &n, 2);
     if (sc_ed25519_sign(author->my_ed25519_privkey, body, 39 + enc_len, body + 39 + enc_len) != SC_OK) return 0;