Erasure encoding availability (#345)

* Erasure encoding availability initial commit

 * Modifications to availability store to keep chunks as well as
   reconstructed blocks and extrinsics.
 * Gossip messages containig signed erasure chunks.
 * Requesting eraure chunks with polkadot-specific messages.
 * Validation of erasure chunk messages.

* Apply suggestions from code review

Co-Authored-By: Luke Schoen <ltfschoen@users.noreply.github.com>

* Fix build after a merge

* Gossip erasure chunk messages under their own topic

* erasure_chunks should use the appropriate topic

* Updates Cargo.lock

* Fixes after merge

* Removes a couple of leftover pieces of code

* Fixes simple stuff from review

* Updates erasure and storage for more flexible logic

* Changes validation and candidate receipt production.

* Adds add_erasure_chunks method

* Fixes most of the nits

* Better validate_collation and validate_receipt functions

* Fixes the tests

* Apply suggestions from code review

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

* Removes unwrap() calls

* Removes ErasureChunks primitive

* Removes redundant fields from ErasureChunk struct

* AvailabilityStore should store CandidateReceipt

* Changes the way chunk messages are imported and validated.

 * Availability store now stores a validator_index and n_validators for
 each relay_parent.
 * Availability store now also stores candidate receipts.
 * Removes importing chunks in the table and moves it into network
 gossip validation.
 * Validation of erasure messages id done against receipts that are
 stored in the availability store.

* Correctly compute topics for erasure messages

* Removes an unused parameter

* Refactors availability db querying into a helper

* Adds the apis described in the writeup

* Adds a runtime api to extract erasure roots form raw extrinsics.

* Adds a barebone BlockImport impl for avalability store

* Adds the implementation of the availability worker

* Fix build after the merge with master.

* Make availability store API async

* Bring back the default wasmtime feature

* Lines width

* Bump runtime version

* Formatting and dead code elimination

* some style nits (#1)

* More nits and api cleanup

* Disable wasm CI for availability-store

* Another nit

* Formatting

polkadot/network/src/collator_pool.rs

@@ -184,7 +184,7 @@ impl CollatorPool {
 	/// The collation should have been checked for integrity of signature before passing to this function.
 	pub fn on_collation(&mut self, collator_id: CollatorId, relay_parent: Hash, collation: Collation) {
 		if let Some((para_id, _)) = self.collators.get(&collator_id) {
-			debug_assert_eq!(para_id, &collation.receipt.parachain_index);
+			debug_assert_eq!(para_id, &collation.info.parachain_index);
 
 			// TODO: punish if not primary? (https://github.com/paritytech/polkadot/issues/213)
 
@@ -279,7 +279,7 @@ mod tests {
 		pool.await_collation(relay_parent, para_id, tx1);
 		pool.await_collation(relay_parent, para_id, tx2);
 		pool.on_collation(primary.clone(), relay_parent, Collation {
-			receipt: CandidateReceipt {
+			info: CandidateReceipt {
 				parachain_index: para_id,
 				collator: primary.clone().into(),
 				signature: Default::default(),
@@ -288,7 +288,8 @@ mod tests {
 				fees: 0,
 				block_data_hash: [3; 32].into(),
 				upward_messages: Vec::new(),
-			},
+				erasure_root: [1u8; 32].into(),
+			}.into(),
 			pov: make_pov(vec![4, 5, 6]),
 		});
 
@@ -307,7 +308,7 @@ mod tests {
 		assert_eq!(pool.on_new_collator(primary.clone(), para_id.clone(), PeerId::random()), Role::Primary);
 
 		pool.on_collation(primary.clone(), relay_parent, Collation {
-			receipt: CandidateReceipt {
+			info: CandidateReceipt {
 				parachain_index: para_id,
 				collator: primary,
 				signature: Default::default(),
@@ -316,7 +317,8 @@ mod tests {
 				fees: 0,
 				block_data_hash: [3; 32].into(),
 				upward_messages: Vec::new(),
-			},
+				erasure_root: [1u8; 32].into(),
+			}.into(),
 			pov: make_pov(vec![4, 5, 6]),
 		});