[Bootstrapping] Spork root block view extends previous spork

[jordanschalm]

Context

The bootstrapping tooling generates a root block for a spork. The root block provides a flag --root-height, which is used to manually pass in the height extending the final block of the prior spork, ensuring block heights are not repeated. By contrast, the block view is reset to 0 every spork, so subsequent sporks re-use view numbers.

In Mainnet25, we released the Protocol KV Store, which includes a view-based mechanism for determining its version over time. The KV Store version cannot be downgraded, and we rely on the fact that views are strictly increasing over time for safety. Currently the KV Store Upgrade mechanism (which also supports "Protocol HCU"s) is incompatible with the current practice of resetting the view count every epoch.

⚠️ Caution: Because views have been reset for a long time, there are known and (we should assume) unknown instances in our codebase where components assume root blocks have a zero view. Here is a non-exhaustive list of examples:

• SealingSegment validation
• ...

Definition of Done

• Implement a mechanism for injecting an initial view into the root block during sporks
  • simplest is a CLI flag + manual process, as we do for height, but it would be great to automate both
• Update components/test which assume spork root blocks have 0 view