message: log when a producing node drops a previously accepted but unapplied transaction from consideration due to expiry
diff: @@ -1073,6 +1073,10 @@ producer_plugin_impl::start_block_result producer_plugin_impl::start_block(bool
  for (auto& trx: unapplied_trxs) {
  auto category = calculate_transaction_category(trx);
  if (category == tx_category::EXPIRED || (category == tx_category::UNEXPIRED_UNPERSISTED && _producers.empty())) {
  + if (!_producers.empty()) {
  + fc_dlog(_trx_trace_log, "[TRX_TRACE] Node with producers configured is dropping a PREVIOUSLY ACCEPTED transaction : ${txid}",
  + ("txid", trx->id));
  + }
  chain.drop_unapplied_transaction(trx);
  } else if (category == tx_category::PERSISTED || (category == tx_category::UNEXPIRED_UNPERSISTED && _pending_block_mode == pending_block_mode::producing)) {
  apply_trxs.emplace_back(std::move(trx));
  