Improve logging and cleanup in miner around block sealing (#10745)

* Stop breaking out of loop if a non-canonical hash is found

* include expected hash in log msg

* More logging

* Scope

* Syntax

* Log in blank RollingFinality
Escalate bad proposer to warning

* Check validator set size: warn if 1 or even number

* More readable code

* Use SimpleList::new

* Extensive logging on unexpected non-canonical hash

* Wording

* wip

* Update ethcore/blockchain/src/blockchain.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Improved logging, address grumbles

* Update ethcore/src/engines/validator_set/simple_list.rs

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

* Report benign misbehaviour iff currently a validator

* Report malicious behaviour iff we're a validator

* Escalate to warning and fix wording

* Test reporting behaviour
Don't require node to be part of the validator set to report malicious behaviour

* Include missing parent hash in MissingParent error

* Update ethcore/src/engines/validator_set/simple_list.rs

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

* docs

* remove unneeded into()
Move check for parent_step == step for clarity&efficiency
Remove dead code for Seal::Proposal

* typo

* Wording

* naming

* WIP

* cleanup

* cosmetics

* cosmetics and one less lvar

* spelling

* Better loggin when a block is already in chain

* More logging

* On second thought non-validators are allowed to report

* cleanup

* remove dead code

* Keep track of the hash of the last imported block

* Let it lock

* Serialize access to block sealing

* Take a lock while sealing a block

* Cleanup

* whitespace

ethcore/sync/src/block_sync.rs

@@ -548,12 +548,18 @@ impl BlockDownloader {
 			let result = if let Some(receipts) = receipts {
 				io.chain().queue_ancient_block(block, receipts)
 			} else {
+				trace_sync!(self, "Importing block #{}/{}", number, h);
 				io.chain().import_block(block)
 			};
 
 			match result {
 				Err(EthcoreError::Import(ImportError::AlreadyInChain)) => {
-					trace_sync!(self, "Block already in chain {:?}", h);
+					let is_canonical = if io.chain().block_hash(BlockId::Number(number)).is_some() {
+						"canoncial"
+					} else {
+						"not canonical"
+					};
+					trace_sync!(self, "Block #{} is already in chain {:?} – {}", number, h, is_canonical);
 					self.block_imported(&h, number, &parent);
 				},
 				Err(EthcoreError::Import(ImportError::AlreadyQueued)) => {