Refreshed BIP324

The email conversation between Murch, Jonas Schnelli, and Anthony Towns discusses the allocation of message IDs in the network with the addition of BIP324. The group considers different ways to increase space while being conservative, including treating the first bit as a 2-byte message ID or using an explicit signaling system. Jonas suggests reserving the short ID 0xFF for 2-byte short IDs, but Pieter notes that it is not needed since the current BIP324 draft already has a mechanism for another command byte following. The group agrees to exclude rarely-sent or at-most-once-sent commands from assigning short IDs. Anthony suggests introducing novel 1-byte messages before allocating them and recommends against reserving a byte for one-shot messages. Finally, Pieter provides statistics on the percentage of sent bytes for commands with 12 bytes or more, which vary depending on the node's inbound and outbound connections.