Updated SDK to align with Protocol 6

[ghost]

Purpose

Update SDK to align with new consensus protocol and hence changes done in gRPC API
Concordium/concordium-grpc-api@13e2394.

This PR at the same time prepare for release 4.0.0.

Changes

• ConsensusInfo
  • SlotDuration is now an nullable field, only present in protocols 1-5.
  • a new field ConcordiumBftDetails is added, that is present if protocol
    version is 6 or higher
  • Bugfix: BlockLastArrivedTime was wrongly mapped from BlockLastReceivedTime.
• BlockInfo
  • BlockSlot is nullable, and only present in protocols 1-5
  • new fields Round and Epoch that are present in protocol 6 or higher.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.

[abizjak]

Looks good.

[abizjak]

Also an emoji 🚀 to fullfil the challenge.