refactor(signer): Add enum for version-specific data to BlockInfo

[jbencin]

Description

Add enum for version-specific (Signer v0 or v1) data to BlockInfo

Applicable issues

• fixes [stacks-signer] seperate common state for v0 and v1 block info out and wrap specific internal state in an enum #4816

Additional info (benefits, drawbacks, caveats)

Checklist

• Test coverage for new or modified code paths
• Changelog is updated
• Required documentation changes (e.g., docs/rpc/openapi.yaml and rpc-endpoints.md for v2 endpoints, event-dispatcher.md for new events)
• New clarity functions have corresponding PR in clarity-benchmarking repo
• New integration test(s) added to bitcoin-tests.yml

[obycode]

LGTM!

[kantai]

I like the idea of using an enum for version specific data here, but I think this breaks v0 at the moment: signed_over is used to indicate whether or not a block has been signed by the local node. Maybe it would make sense to add a new field to the v0 enum for this, or maybe the signed_over field should just move back into the common struct.