Remove some unreferenced fields from TestState

  BIO *async_bio = nullptr;

  // packeted_bio is the packeted BIO which simulates read timeouts.

  BIO *packeted_bio = nullptr;

  bssl::UniquePtr<EVP_PKEY> channel_id;

  bool cert_ready = false;

  bssl::UniquePtr<SSL_SESSION> session;

  bssl::UniquePtr<SSL_SESSION> pending_session;

  bool early_callback_called = false;

  bool handshake_done = false;

  // private_key is the underlying private key used when testing custom keys.

  bssl::UniquePtr<EVP_PKEY> private_key;

  std::vector<uint8_t> private_key_result;

  // private_key_retries is the number of times an asynchronous private key

  // operation has been retried.

  unsigned private_key_retries = 0;

  bool got_new_session = false;

  bssl::UniquePtr<SSL_SESSION> new_session;

  bool ticket_decrypt_done = false;