Hash and sign only when app says so

[lpetrovic05]

depends on #17463

Once handleConsensusRound returns a boolean, the platform should be modified to sign states only when the app returns true. We should still hash every state. A testing app can be modified to test this feature.

[poulok]

We changed the epic ticket to hash EVERY state like we do today, but only to sign the state the app says to. The state hashing algorithm currently depends on every state being hashed, so we will keep it like that until we have cycles to adjust it.