* 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
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