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* Delete outdated tests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>

eth2/types/Cargo.toml

@@ -38,6 +38,7 @@ rand_xorshift = "0.2.0"
 cached_tree_hash = { path = "../utils/cached_tree_hash" }
 serde_yaml = "0.8.11"
 tempfile = "3.1.0"
+rusqlite = { version = "0.22.0", features = ["bundled"], optional = true }
 arbitrary = { version = "0.4.4", features = ["derive"], optional = true }
 
 [dev-dependencies]
@@ -46,6 +47,8 @@ serde_json = "1.0.52"
 criterion = "0.3.2"
 
 [features]
+default = ["sqlite"]
+sqlite = ["rusqlite"]
 arbitrary-fuzz = [
   "arbitrary",
   "ethereum-types/arbitrary",