[BFT] Refactor "full DKG info" in bootstrapping process

[durkmurder]

since we are mentioning the "full DKG info" here, I would be inclined to include the indexMap. Feel free to skip, but if it is easy and doesn't break other stuff, I think we should persist the indexMap too.

Originally posted by @AlexHentschel in #6424 (comment)

Currently EncodableFullDKG doesn't include IndexMap and generally has a dangerous structure for serialization where private keys and public keys needs to be ordered in same way. As a proposal refactor EncodableFullDKG to include index map as well as group participant data in single structure and encode list of those structures instead of decomposing each field into a slice.