BiBo changes in CU

[TillaTheHun0]

• initial state is simply null
• tags passed to the handler are now just the raw array of { name, value } objects, from Arweave
  • Test contracts will need to use new format for tags
• handler now accepts (buffer, message, ao)
  • setting up handler returns a Promise
  • invoking the handler does not return a Promise
• Persist state as buffer instead of object, as part of eval
  • update zod schemas