feat(arbitrum): light client

[benluelo]

• add Arbitrum to chain-utils
• add Arbitrum to block-message
• add Arbitrum to relay-message
• create proto definitions for light client
• arbitrum-verifier
  • untested, will add testdata in followup pr
• arbitrum-light-client
• docs on how the light client and state tracking works
  • do NOT let me merge this PR without this one checked off. I promise you I will try
  • this is documented in arbitrum.proto

Other misc. changes made in this PR:

• implement IntoIterator<Item = u8> for byte array wrapper types directly
• tracing improvements
• a few ICEs for good measure
• start exposing useful fetching actions via the cli (query latest height) both generically and for specific chains
• add chain id to all voyager logs (where applicable)
• clean up error types in ethereum-verifier and arbitrum-verifier (print full error stack since cosmwasm doesn't call .source() on the error type, it just uses Display)
• devnet-union proposal period is now 30 seconds, not 2 days