chore: update predicate status format for easier parsing

[MicaiahReid]

Description

Previously, a serialized PredicateStatus would have the format:

{ "scanning": { "last_evaluated_block": ... }

where the predicate status type is the key that points to the data. This PR changes this format to be:

{
  "type": "scanning",
  "info": { "last_evaluated_block": ... }
}

Checklist

• All tests pass

[lgalabru]

Good idea, thanks!

[BLuEScioN]

Thanks for doing this. This helps