* Update to spec v0.9.0
* Update to v0.9.1
* Bump spec tags for v0.9.1
* Formatting, fix CI failures
* Resolve accidental KeyPair merge conflict
* Document new BeaconState functions
* Fix incorrect cache drops in `advance_caches`
* Update fork choice for v0.9.1
* Clean up some FIXMEs
* Fix a few docs/logs
* Add basic block processing benches
* Start reviving state processing benches
* Fix old block builders
* Add optimization for faster pubkey add
* Tidy benches, add another
* Add extra block processing bench
* Start working on faster BLS scheme
* Add partially complete sig verify optimization
* Add .gitignore to state processing
* Add progress on faster signature verification
* Fix SignatureSet for fake_crypto
* Tidy attester slashings sig set
* Tidy bulk signature verifier
* Refactor signature sets to be cleaner
* Start threading SignatureStrategy through code
* Add (empty) test dir
* Move BenchingBlockBuilder
* Add initial block signature verification tests
* Add tests for bulk signature verification
* Start threading SignatureStrategy in block proc.
* Refactor per_block_processing errors
* Use sig set tuples instead of lists of two
* Remove dead code
* Thread VerifySignatures through per_block_processing
* Add bulk signature verification
* Introduce parallel bulk signature verification
* Expand state processing benches
* Fix additional compile errors
* Fix issue where par iter chunks is 0
* Update milagro_bls dep
* Remove debugs, code fragment in beacon chain
* Tidy, add comments to block sig verifier
* Fix various PR comments
* Add block_root option to per_block_processing
* Fix comment in block signature verifier
* Fix comments from PR review
* Remove old comment
* Fix comment
The `latest_block_root` input argument was unnecessary as we were always setting it to something
almost equivalent to `state.latest_block_root` anyway, and more importantly, it was messing up the
caching of the state root. Previously it was possible for the function to update the state's latest
block root, and then hash the outdated block root that was passed in as an argument.
