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Closes #2923

Caches the block hash to ensure we only compute it once in consensus
execution.

---

#### PR checklist

- [x] Tests written/updated - not sure what test I should write, any
suggestions?
- [x] Changelog entry added in `.changelog` (we use
[unclog](https://github.com/informalsystems/unclog) to manage our
changelog)
- [ ] Updated relevant documentation (`docs/` or `spec/`) and code
comments
- [x] Title follows the [Conventional
Commits](https://www.conventionalcommits.org/en/v1.0.0/) spec

(cherry picked from commit 1b16d91)