New sessions, kill consensus module (#2802)

* Draft of new sessions

* Reintroduce tuple impls

* Move staking module to new session API

* More work on staking and grandpa.

* Use iterator to avoid cloning and tuple macro

* Make runtime build again

* Polish the OpaqueKeys devex

* Move consensus logic into system & aura.

* Fix up system module

* Get build mostly going. Stuck at service.rs

* Building again

* Update srml/staking/src/lib.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Refactoring out Consensus module, AuthorityIdOf, &c.

* Refactored out DigestItem::AuthoritiesChanged. Building.

* Remove tentative code

* Remove invalid comment

* Make Seal opaque and introduce nice methods for handling opaque items.

* Start to use proper digest for Aura authorities tracking.

* Fix up grandpa, remove system::Raw/Log

* Refactor Grandpa to use new logging infrastructure.

Also make authorityid/sessionkey static. Switch over to storing
authorities in a straight Vec.

* Building again

* Tidy up some AuthorityIds

* Expunge most of the rest of the AuthorityKey confusion.

Also, de-generify Babe and re-generify Aura.

* Remove cruft

* Untangle last of the `AuthorityId`s.

* Sort out finality_tracker

* Refactor median getting

* Apply suggestions from code review

Co-Authored-By: Robert Habermeier <rphmeier@gmail.com>

* Session tests works

* Update core/sr-primitives/src/generic/digest.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Session tests works

* Fix for staking from @dvc94ch

* log an error

* fix test runtime build

* Some test fixes

* Staking mock update to new session api.

* Fix build.

* Move OpaqueKeys to primitives.

* Use on_initialize instead of check_rotate_session.

* Update tests to new staking api.

* fixup mock

* Fix bond_extra_and_withdraw_unbonded_works.

* Fix bond_with_little_staked_value_bounded_by_slot_stake.

* Fix bond_with_no_staked_value.

* Fix change_controller_works.

* Fix less_than_needed_candidates_works.

* Fix multi_era_reward_should_work.

* Fix nominating_and_rewards_should_work.

* Fix nominators_also_get_slashed.

* Fix phragmen_large_scale_test.

* Fix phragmen_poc_works.

* Fix phragmen_score_should_be_accurate_on_large_stakes.

* Fix phragmen_should_not_overflow.

* Fix reward_destination_works.

* Fix rewards_should_work.

* Fix sessions_and_eras_should_work.

* Fix slot_stake_is_least_staked_validator.

* Fix too_many_unbond_calls_should_not_work.

* Fix wrong_vote_is_null.

* Fix runtime.

* Fix wasm runtime build.

* Update Cargo.lock

* Fix warnings.

* Fix grandpa tests.

* Fix test-runtime build.

* Fix template node build.

* Fix stuff.

* Update Cargo.lock to fix CI

* Re-add missing AuRa logs

Runtimes are required to know about every digest they receive ― they
panic otherwise.  This re-adds support for AuRa pre-runtime digests.

* Update core/consensus/babe/src/digest.rs

Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

* Kill log trait and all that jazz.

* Refactor staking tests.

* Fix ci runtime wasm check.

* Line length 120.

* Make tests build again

* Remove trailing commas in function declarations

The `extern_functions!` macro doesn’t like them, perhaps due to a bug in
rustc.

* Fix type error

* Fix compilation errors

* Fix a test

* Another couple of fixes

* Fix another test

* More test fixes

* Another test fix

* Bump runtime.

* Wrap long line

* Fix build, remove redundant code.

* Issue to track TODO

* Leave the benchmark code alone.

* Fix missing `std::time::{Instant, Duration}`

* Indentation

* Aura ConsensusLog as enum

substrate/core/sr-primitives/src/testing.rs

@@ -19,12 +19,12 @@
 use serde::{Serialize, Serializer, Deserialize, de::Error as DeError, Deserializer};
 use std::{fmt::Debug, ops::Deref, fmt};
 use crate::codec::{Codec, Encode, Decode};
-use crate::traits::{self, Checkable, Applyable, BlakeTwo256, Convert};
+use crate::traits::{self, Checkable, Applyable, BlakeTwo256, OpaqueKeys};
+use crate::generic;
 use crate::weights::{Weighable, Weight};
-use crate::generic::DigestItem as GenDigestItem;
 pub use substrate_primitives::H256;
 use substrate_primitives::U256;
-use substrate_primitives::sr25519::{Public as AuthorityId, Signature as AuthoritySignature};
+use substrate_primitives::ed25519::{Public as AuthorityId};
 
 /// Authority Id
 #[derive(Default, PartialEq, Eq, Clone, Encode, Decode, Debug)]
@@ -37,39 +37,19 @@ impl Into<AuthorityId> for UintAuthorityId {
 	}
 }
 
-/// Converter between u64 and the AuthorityId wrapper type.
-pub struct ConvertUintAuthorityId;
-impl Convert<u64, Option<UintAuthorityId>> for ConvertUintAuthorityId {
-	fn convert(a: u64) -> Option<UintAuthorityId> {
-		Some(UintAuthorityId(a))
-	}
+impl OpaqueKeys for UintAuthorityId {
+	fn count() -> usize { 1 }
+	// Unsafe, i know, but it's test code and it's just there because it's really convenient to
+	// keep `UintAuthorityId` as a u64 under the hood.
+	fn get_raw(&self, _: usize) -> &[u8] { unsafe { &std::mem::transmute::<_, &[u8; 8]>(&self.0)[..] } }
+	fn get<T: Decode>(&self, _: usize) -> Option<T> { self.0.using_encoded(|mut x| T::decode(&mut x)) }
 }
+
 /// Digest item
-pub type DigestItem = GenDigestItem<H256, AuthorityId, AuthoritySignature>;
+pub type DigestItem = generic::DigestItem<H256>;
 
 /// Header Digest
-#[derive(Default, PartialEq, Eq, Clone, Serialize, Debug, Encode, Decode)]
-pub struct Digest {
-	/// Generated logs
-	pub logs: Vec<DigestItem>,
-}
-
-impl traits::Digest for Digest {
-	type Hash = H256;
-	type Item = DigestItem;
-
-	fn logs(&self) -> &[Self::Item] {
-		&self.logs
-	}
-
-	fn push(&mut self, item: Self::Item) {
-		self.logs.push(item);
-	}
-
-	fn pop(&mut self) -> Option<Self::Item> {
-		self.logs.pop()
-	}
-}
+pub type Digest = generic::Digest<H256>;
 
 /// Block Header
 #[derive(PartialEq, Eq, Clone, Serialize, Debug, Encode, Decode)]
@@ -92,7 +72,6 @@ impl traits::Header for Header {
 	type Number = u64;
 	type Hashing = BlakeTwo256;
 	type Hash = H256;
-	type Digest = Digest;
 
 	fn number(&self) -> &Self::Number { &self.number }
 	fn set_number(&mut self, num: Self::Number) { self.number = num }
@@ -106,15 +85,15 @@ impl traits::Header for Header {
 	fn parent_hash(&self) -> &Self::Hash { &self.parent_hash }
 	fn set_parent_hash(&mut self, hash: Self::Hash) { self.parent_hash = hash }
 
-	fn digest(&self) -> &Self::Digest { &self.digest }
-	fn digest_mut(&mut self) -> &mut Self::Digest { &mut self.digest }
+	fn digest(&self) -> &Digest { &self.digest }
+	fn digest_mut(&mut self) -> &mut Digest { &mut self.digest }
 
 	fn new(
 		number: Self::Number,
 		extrinsics_root: Self::Hash,
 		state_root: Self::Hash,
 		parent_hash: Self::Hash,
-		digest: Self::Digest,
+		digest: Digest,
 	) -> Self {
 		Header {
 			number,