Change /contracts/searchForever format from:

{
  created: [C1, C2],
  archived: [A1, A2]
}

to

[
  {created: C1},
  {created: C2},
  {archived: A1},
  {archived: A2},
  {error: E1}
]

I'd prefer if the encoding is the same for both endpoints. Since the /commands/exercise endpoint does not work with the first format, we need to use the second in both places. It would be nice if could keep the order of the events we don't filter out during consolidation for the /contracts/searchForever endpoint, but I don't consider it a hard requirement.

Originally posted by @hurryabit in #3936