refactor and free storage

[rueshyna]

change:

• remove "inline" annotation
• remove "Execute" case from proposal content, the replacement is Execute_lambda
• the interface of Execute_lambda of proposal_content is change.
  • remove option for lambda
  • the type of lambda support return list. unit -> operation list
• the function signature of sign_proposal is all change in bytes for consistance
• add annotation for event and parameter
• proposal_id
  • rename as challenge_id
  • type is bytes instead
• additional big_map for archive proposals
  • big_map archives only state.
  • The full state of proposal will emit as an event. UI can retrieve history here.
• add update_metadata entrypoint

cc: @tj825

[JulesGuesnon]

LGTM