feat: Minor extensions for server interoperability

[slowli]

What ❔

• Simplifies generating executor configurations.
• Adds byte conversions for BlockHeaderHash.
• Makes SyncBlocks actor terminate successfully on context cancellation.

Why ❔

Part of preparations for the integration with the server codebase.

[pompon0]

Are you sure we need this? Perhaps we can make it just easier to generate well-signed blocks?

[slowli]

Are you sure we need this? Perhaps we can make it just easier to generate well-signed blocks?

I thought that was the approach we agreed upon. For tests / initial PoC it would be easy to generate well-signed blocks, but for production, we'd need to introduce key management and reliably broadcast information about the validator set (I guess using L1 smart contracts). @brunoffranca WDYT?

[brunoffranca]

Hey, if you guys think it's easier to introduce well-signed blocks now, then it's fine by me. It seemed simpler to me at the time to just turn off QC validation. But at the time I also thought we were not going to be running the consensus actor at all.

[pompon0]

please remember to address "block_hash:" -> "block_header_hash:"