Implement Slashing Protection (#1116)

* Implement slashing protection

Roll-up of #588 with some conflicts resolved

* WIP improvements

* Require slot uniqueness for blocks (rather than epochs)
* Native DB support for Slot and Epoch
* Simplify surrounding/surrounded-by queries

* Implement unified slashing protection database

A single SQL database saves on open file descriptors.

* Make slashing protection concurrency safe.

Revive tests, add parallel tests.

* Some simplifications

* Auto-registration, test clean-ups

* More tests, clean-ups, hardening

* Fix comments in BLS

* Optimise bulk validator registration

* Delete outdated tests

* Use bundled SQLite in slashing protection

* Auto-register validators in simulation

* Use real signing_root in slashing protection

* Update book for --auto-register

* Refine log messages and help flags

* Correct typo in Cargo.toml authors

* Fix merge conflicts

* Safer error handling in sqlite slot/epoch

* Address review comments

* Add attestation test mutating block root

Co-authored-by: pscott <scottpiriou@gmail.com>

validator_client/slashing_protection/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "slashing_protection"
+version = "0.1.0"
+authors = ["Michael Sproul <michael@sigmaprime.io>", "pscott <scottpiriou@gmail.com>"]
+edition = "2018"
+
+[dependencies]
+tempfile = "3.1.0"
+types = { path = "../../eth2/types" }
+tree_hash = { path = "../../eth2/utils/tree_hash" }
+rusqlite = { version = "0.22.0", features = ["bundled"] }
+r2d2 = "0.8.8"
+r2d2_sqlite = "0.15"
+parking_lot = "0.9.0"
+
+[dev-dependencies]
+rayon = "1.3.0"