feat: publish instanceID during peer comms

[kentquirk]

Which problem is this PR solving?

This is an alternative implementation of #1417, with 2 key differences:

• Added a new generic type, MapWithTTL to store the ID and address and used it instead of SetWithTTL. It's about 15% slower than SetWithTTL for equivalent operations, but it solves the problem we have here.
• I constrained the unique ID to 8 characters, hashed from a UUID.
• I also cleaned up an unneeded typename in main.go that my editor was complaining about.

Closes #1417.

[MikeGoldsmith]

Looks good, just one suggestion to make the hash seed a little clearer.