Refreshed BIP324

In an email conversation, Pieter expressed his thoughts on a uniform encoding scheme for message identifiers in the p2p protocol. He suggested that there is no strict need to distinguish between short-binary and long-alphabetic commands and that some short commands could be treated as aliases for old long-alphabetic ones. However, Anthony questioned whether this approach optimizes for the right goals. He asserted that the goals should be to make it easy to come up with a message identifier without accidentally conflicting with someone else's proposal and to ensure commonly used messages on the wire have a short encoding to save bandwidth. He also pointed out that picking a value from a set of 102 elements could produce conflicts. Pieter clarified that he meant the scheme as an encoding scheme, not a replacement for negotiation/coordination mechanism. He thought having a uniform encoding scheme without explicit distinction between "short commands" and "long commands" would be interesting at that layer. He added that there could still be an initial assignment for 1-byte encodings or an explicit mechanism to negotiate other assignments, or nothing at all for now. In conclusion, Pieter acknowledged that his suggestion may be more complexity than the alternative and that the alternative already has a working implementation and written-up specification.