* zebra-chain changes from the subtree-boundaries branch
```sh
git checkout -b subtree-boundaries-zebra-chain main
git checkout origin/subtree-boundaries zebra-chain
git commit
```
* Temporarily populate new subtree fields with None - for revert
This temporary commit needs to be reverted in the next PR.
* Applies suggestions from code review
* removes from_repr_unchecked methods
* simplifies loop
---------
Co-authored-by: arya2 <aryasolhi@gmail.com>
* Split disk reads from CPU-heavy Sprout interstitial tree cryptography
* Improve anchor validation debugging and error messages
* Work around a test data bug, and save some CPU
* Remove redundant checks for empty shielded data
* Skip generating unused interstitial treestates
* Do disk fetches and quick checks, then CPU-heavy cryptography
* Wrap HistoryTree in an Arc in the state
* Run CPU-intensive chain validation and updates in parallel rayon threads
* Refactor to prepare for parallel tree root calculations
* Run finalized state note commitment tree root updates in parallel rayon threads
* Update finalized state note commitment trees using parallel rayon threads
* Fix a comment typo and add a TODO
* Split sprout treestate fetch into its own function
* Move parallel note commitment trees to zebra-chain
* Re-calculate the tree roots in the same parallel batches
* Do non-finalized note commitment tree updates in parallel threads
* Update comments about note commitment tree rebuilds
* Do post-fork tree updates in parallel threads
* Add a TODO for parallel tree updates in tests
* Fix broken intra-doc links
* Clarify documentation for sprout treestates
* Sort Cargo.toml dependencies
teor