Match BlockError into penalty in block gossip

[dapplion]

Issue Addressed

In process_gossip_unverified block we match the verification error and we should always:

• log something
• propagate_validation_result to libp2p

However, for some variants we don't do that. This PR refactors the match to always:

• Log something (at least one debug log per error)
• propagate_validation_result to libp2p
• Explicitly specify a penalty or set the penalty to None (force you to think about it)

If others thumbs up this style I can extend to the other gossip messages. This style makes gossip handling more consistent and less chance of forgetting to propagate results or penalize peers.

For some variants like Slashable we penalize the peer in our internal scoring but we don't penalize in the gossip layer. This is odd, anyone knows why?

[pawanjay176]

I like this pattern. Easier to keep track