Include parent head in CandidateReceipt (#826)

* runtime: candidate receipt must pass parent head

* construct parachain candidates using correct parent_head

* validate that the parent header is correct in candidate receipt

* fix test fallout

* bump runtime versions

polkadot/network/src/collator_pool.rs

@@ -285,6 +285,7 @@ mod tests {
 				collator: primary.clone().into(),
 				signature: Default::default(),
 				head_data: HeadData(vec![1, 2, 3]),
+				parent_head: HeadData(vec![]),
 				egress_queue_roots: vec![],
 				fees: 0,
 				block_data_hash: [3; 32].into(),
@@ -314,6 +315,7 @@ mod tests {
 				collator: primary,
 				signature: Default::default(),
 				head_data: HeadData(vec![1, 2, 3]),
+				parent_head: HeadData(vec![]),
 				egress_queue_roots: vec![],
 				fees: 0,
 				block_data_hash: [3; 32].into(),

polkadot/network/src/gossip.rs

@@ -906,6 +906,7 @@ mod tests {
 			parachain_index: 5.into(),
 			collator: [255; 32].unchecked_into(),
 			head_data: HeadData(vec![9, 9, 9]),
+			parent_head: HeadData(vec![]),
 			signature: Default::default(),
 			egress_queue_roots: Vec::new(),
 			fees: 1_000_000,

polkadot/network/src/tests/mod.rs

@@ -173,6 +173,7 @@ fn fetches_from_those_with_knowledge() {
 		parachain_index: 5.into(),
 		collator: [255; 32].unchecked_into(),
 		head_data: HeadData(vec![9, 9, 9]),
+		parent_head: HeadData(vec![]),
 		signature: Default::default(),
 		egress_queue_roots: Vec::new(),
 		fees: 1_000_000,