tx_pool: revert #4592 and move bin2hex conversion to on_get_transaction_pool

src/rpc/core_rpc_server.cpp

@@ -924,6 +924,8 @@ namespace cryptonote
       return r;
 
     m_core.get_pool_transactions_and_spent_keys_info(res.transactions, res.spent_key_images, !request_has_rpc_origin || !m_restricted);
+    for (tx_info& txi : res.transactions)
+      txi.tx_blob = epee::string_tools::buff_to_hex_nodelimer(txi.tx_blob);
     res.status = CORE_RPC_STATUS_OK;
     return true;
   }