Stake events should emit JSON

[autholykos]

This item pertains to "implement stake events changes". To be discussed with @herr-seppia

[autholykos]

There is a dependency on what Piecrust can do

[herr-seppia]

There is a dependency on what Piecrust can do

Piecrust features shipped and imported into rusk

[herr-seppia]

I don't know it this worth.
Emitting events in JSON add a bit overhead (and code complexity) for json serialization and deserialization.

Furthermore, if we are going to connect consensus to stake events we'are going to introduce deserialization costs (current rkyv events are already deserialized)

[herr-seppia]

Closing, as the rkyv/json should be implemented by the archiver (if needed)