DSQ messages are 142 bytes.
Previously, assuming a relatively highly connected masternode hosting 100 connection, each round of coinjoin will result in 14.2KB (100*142) of inbound and outbound traffic each.
Now, using the inventory system, a message will first use 36 bytes per peer (sending and receiving), plus the size of a `getdata` message and the actual message itself. As a result, bandwidth usage for 1 round of mixing would be closer to 36 * 100 + 142 (dsq) + 36 (getdata) = ~3.8KB, a reduction of around ~73%
