Implement validators for the DHT values

[rach-id]

As specified in the P2P ADR #66, we will use record validators to validate the values posted on the DHT. These values will be either DataCommitmentConfirms or ValsetConfirms. Thus, we could run stateless checks on them to add an extra layer of security when posting/querying for confirms.

• Implement ValsetConfirms validator #72
• Implement DataCommitementConfirms validator #73
• Signing over random digest problem #225
• Valset confirm validator verify signature #224