Parse raw QC when receiving messages

[yacovm]

QuorumCertificates were carried around the network already parsed, which forced parsing to happen before a message reached the epoch.

Since a QC has an ability to verify its own signature, it implicitly means that a QC implementation needs knowledge of the public keys for the epoch the QC was created for.

To that end, we introduce a new type - RawQuorumCertificate, and corresponding types for message handling (RawNotarization, RawEmptyNotarization, RawNotarization, RawQuorumRound).

Message and ReplicationResponse now carry these on the wire, while Raw() helpers convert verified types to raw when sending/broadcasting

Parsing now happens on the receive path:

• QCDeserializer gains ParseQuorumCertificate(RawQuorumCertificate); a new QCDeserializerCreator builds a deserializer per epoch from the node set (Node now carries its PK)
• handleRaw{Notarization,EmptyNotarization,Finalization}Message parse the raw QC into a verified QC before delegating to the existing handlers; parse failures are logged and the message is dropped
• RawQuorumRound.ToQuorumRound parses rounds in replication responses
• Epoch holds a runtime qcDeserializer built via init()

This ensures that in order to verify a QC signature we need to know the node public keys that correspond to the QC.