Remove separation of key fields from value during marshalling

[rigelrozanski]

As per several discussions, to simplify the code we should allow for duplicate fields to be stored in both the key and value of a key value pair, this is already the case in most places I believe, however we'd started decoupling these within staking. For example a validator's key uses the the validators operating address, which is also a field in the Validator object and thus also included in the value... decoupling this creates extra code maintenance (and possibility of errors) as these structs change.