CIP-180 | Block Producer Identification

Allow producers to identify their node implementation and version, similar to HTTP user-agent strings.

- Add informational_dataset structure as 6th block element
- provide examples for different node implementations
- Supports testnet build metadata examples (+leios, +peras, +mithril)
- Includes CBOR encoding examples
- Match Ethereum graffiti precedent (32 bytes)

Co-authored-by: Adam Dean <adam@crypto2099.io>
Co-authored-by: Robert Phair <rphair@cosd.com>
Co-authored-by: Sebastian Nagel <ch1bo@users.noreply.github.com>

Author: 4 people