* Fix parallelism bug in exit processing
Also:
* Remove parallelism for all other operations except deposit merkle proofs
* Improve exit tests
* Fix broken attestation test
Closes#1090
* Allow for generating block/pre/post states from some unit tests (#1123)
* Add post-state checks, comments
* Add state_transition_vectors crate
* Integrate new testing crate with CI
* Add readme
* Add additional valid tests
* Remove ExitTests (they were moved to new crate)
* Small test fixes
* Delete incorrect saturating_sub in slash_validator
And clean-up the balance increase/decrease functions to look more like the spec.
Co-authored-by: Paul Hauner <paul@paulhauner.com>
