add slotId and kyc fields to all candidates

[wpank]

• adds a unique slotId to all candidates which should help in maintaining consistency
• adds a kyc field to candidates that don't already have one (defaults to false)
• Nothing else is changed for any candidates besides adding those fields for everyone where they don't already exist

This should be merged before #2586 , so that the new CI checks introduced in that PR will pass (as it checks that all those fields exist on all candidates)