Introduce inherent digests (#2466)

* Introduce inherent digests

* Implement inherent digests

* fix silly error

* Implementation of inherent digests in BABE

All tests pass. There are still limitations:

1. The runtime strips out inherent digests, so BABE must re-add them.
2. The test runtime checks that it can re-compute all digests.  It
   can’t, so I had to comment out that test.

* Fix compilation and seal import

Seals were not imported correctly: the pre-digest was imported twice,
instead of both it and the seal being imported.  Also, other parts of
the code did not compile due to incomplete refactoring.

* Remove bogus assertion

* Fix testsuite compilation

* Remove unused import

* Fix compiler diagnostics

* Add inherent digest parameters to block constructors

This enforces that inherent digests are added first.

* Fixup Cargo.lock

* Fix build errors

* Re-add an incorrectly removed import

* Bump primitive-types version

* Update Cargo.lock

* Refactoring

* Use inherent digests for AuRa

They do reach the runtime, but get stripped.  I have not figured out
where.

* Fix compilation errors

* Fix compilation errors due to incorrect types

* Fix whitespace

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Add preamble

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Fix silly compile error

* Refactor pre-digest finding code into a separate function

* Remove unwanted assertion

It is too likely to bring down the entire blockchain.

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Use `find_pre_digest` after runtime, too

Also, use `Member` trait rather than rolling our own requirements.

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Fix various warnings

mostly due to upgrading the dependency on `error_chain`.

* Pre-digests nearly complete

This nearly completes the implementation of pre-runtime digests.

* `Seal2` → `Seal` and fix test suite

* Try to fix the storage error

* Try to fix storage (again)

* Fix tests

* Hopefully finish pre-runtime digests

The key is to pass *only* the pre-runtime digests to the runtime.  The
others must be stripped out by `initialize_block`.

* Fix silly typo

* Fix another silly mistake

* Remove unnecessary filtering of BABE pre-digests

We no longer get duplicate BABE pre-digests, so if they appear, the
header should be rejected outright.

* Update Cargo.lock files

* Reformatting

* Fix silly typo in inherent digest code

Also, revert `error.rs` files that contained calls to the `error_chain!`
macro.

* Try to keep the runtime from stripping pre-digests

Currently runs into the “Storage root must match that calculated”
assertion.

* Don’t compute storage root until storage changes are done.

Also, fix a compilation error.

* Fix compile-time error

* Fix compilation errors

* Fix more compile errors

* Hopefully it compiles this time…

* Fix compilation and add docs

* Prevent BABE from adding duplicate pre-runtime digests

Found by comparing with the AuRa code.  I also did some refactoring.

* Respond to review and fix some warnings

* Delete some dead code introduced earlier

* More dead code goes away

* `ref mut` → `&mut`

* Respond to review and fix some warnings

* Fix compilation error

* Remove unneeded `HashT` type parameter

Suggested-by: Robert Habermeier <robert@parity.io>

* Remove spurious #[allow(deprecated)]

* Document inherent digest parameter to `build_block`

* Delete `Simple` trait

It wasn’t needed

* delete wrongly added files

* Fix trait bounds

* Digest serialization tests

I also did some reformatting and cleanup.

* Apply suggestions from code review

Reformatting

Co-Authored-By: André Silva <andre.beat@gmail.com>

* Swap two arguments to `propose` and `propose_with`

Also, remove some needless unsafe code.

* Remove bogus `#![allow(deprecated)]` annotations

With the removal of the deprecated `Seal` variant, these are not needed.

* Add a missing `#[allow(deprecated)]` in the AuRa tests

* Fix silly compile error

* Fix silly compiler error

RLS did not tell me that I hadn’t fixed `babe/lib.rs`, so I missed it.

* Fixes made automatically by Cargo

substrate/core/rpc/src/chain/tests.rs

@@ -68,7 +68,7 @@ fn should_return_a_block() {
 		subscriptions: Subscriptions::new(remote),
 	};
 
-	let block = api.client.new_block().unwrap().bake().unwrap();
+	let block = api.client.new_block(Default::default()).unwrap().bake().unwrap();
 	let block_hash = block.hash();
 	api.client.import(BlockOrigin::Own, block).unwrap();
 
@@ -138,7 +138,7 @@ fn should_return_block_hash() {
 		Ok(None)
 	);
 
-	let block = client.client.new_block().unwrap().bake().unwrap();
+	let block = client.client.new_block(Default::default()).unwrap().bake().unwrap();
 	client.client.import(BlockOrigin::Own, block.clone()).unwrap();
 
 	assert_matches!(
@@ -172,7 +172,7 @@ fn should_return_finalized_hash() {
 	);
 
 	// import new block
-	let builder = client.client.new_block().unwrap();
+	let builder = client.client.new_block(Default::default()).unwrap();
 	client.client.import(BlockOrigin::Own, builder.bake().unwrap()).unwrap();
 	// no finalization yet
 	assert_matches!(
@@ -205,7 +205,7 @@ fn should_notify_about_latest_block() {
 		// assert id assigned
 		assert_eq!(core.block_on(id), Ok(Ok(SubscriptionId::Number(1))));
 
-		let builder = api.client.new_block().unwrap();
+		let builder = api.client.new_block(Default::default()).unwrap();
 		api.client.import(BlockOrigin::Own, builder.bake().unwrap()).unwrap();
 	}
 
@@ -236,7 +236,7 @@ fn should_notify_about_finalized_block() {
 		// assert id assigned
 		assert_eq!(core.block_on(id), Ok(Ok(SubscriptionId::Number(1))));
 
-		let builder = api.client.new_block().unwrap();
+		let builder = api.client.new_block(Default::default()).unwrap();
 		api.client.import(BlockOrigin::Own, builder.bake().unwrap()).unwrap();
 		api.client.finalize_block(BlockId::number(1), None, true).unwrap();
 	}

substrate/core/rpc/src/state/tests.rs

@@ -99,7 +99,7 @@ fn should_notify_about_storage_changes() {
 		// assert id assigned
 		assert_eq!(core.block_on(id), Ok(Ok(SubscriptionId::Number(1))));
 
-		let mut builder = api.client.new_block().unwrap();
+		let mut builder = api.client.new_block(Default::default()).unwrap();
 		builder.push_transfer(runtime::Transfer {
 			from: AccountKeyring::Alice.into(),
 			to: AccountKeyring::Ferdie.into(),
@@ -134,7 +134,7 @@ fn should_send_initial_storage_changes_and_notifications() {
 		// assert id assigned
 		assert_eq!(core.block_on(id), Ok(Ok(SubscriptionId::Number(1))));
 
-		let mut builder = api.client.new_block().unwrap();
+		let mut builder = api.client.new_block(Default::default()).unwrap();
 		builder.push_transfer(runtime::Transfer {
 			from: AccountKeyring::Alice.into(),
 			to: AccountKeyring::Ferdie.into(),
@@ -168,7 +168,7 @@ fn should_query_storage() {
 		let api = State::new(client.clone(), Subscriptions::new(core.executor()));
 
 		let add_block = |nonce| {
-			let mut builder = client.new_block().unwrap();
+			let mut builder = client.new_block(Default::default()).unwrap();
 			builder.push_transfer(runtime::Transfer {
 				from: AccountKeyring::Alice.into(),
 				to: AccountKeyring::Ferdie.into(),