babe: pass epoch data via intermediates (#4807)

* babe: pass epoch data via intermediates

* Switch to use Box<dyn Any> for intermediates

* Set intermediate.epoch to be Option

* Fix proposer should put out an empty intermediate

* Remove unnecessary encode/decode

* Add EpochData to block_import_params in slot worker

* Fix aura compile

* Fix integration test

substrate/client/consensus/babe/src/tests.rs

@@ -565,8 +565,18 @@ fn propose_and_import_block<Transaction>(
 		],
 	};
 
+	let parent_hash = parent.hash();
+
 	let mut block = futures::executor::block_on(proposer.propose_with(pre_digest)).unwrap().block;
 
+	let epoch = proposer_factory.epoch_changes.lock().epoch_for_child_of(
+		descendent_query(&*proposer_factory.client),
+		&parent_hash,
+		*parent.number(),
+		slot_number,
+		|slot| proposer_factory.config.genesis_epoch(slot)
+	).unwrap().unwrap();
+
 	let seal = {
 		// sign the pre-sealed hash of the block and then
 		// add it to a digest item.
@@ -593,7 +603,14 @@ fn propose_and_import_block<Transaction>(
 			storage_changes: None,
 			finalized: false,
 			auxiliary: Vec::new(),
-			intermediates: Default::default(),
+			intermediates: {
+				let mut intermediates = HashMap::new();
+				intermediates.insert(
+					Cow::from(INTERMEDIATE_KEY),
+					Box::new(BabeIntermediate { epoch }) as Box<dyn Any>,
+				);
+				intermediates
+			},
 			fork_choice: Some(ForkChoiceStrategy::LongestChain),
 			allow_missing_state: false,
 			import_existing: false,