Benchmark Ethereum Pallet (#149)

* Add skeleton for worst case import_unsigned_header

* Fix a typo

* Add benchmark test for best case unsigned header import

* Add finality verification to worst case bench

* Move `insert_header()` from mock to test_utils

Allows the benchmarking code to use this without having to pull it in from the mock.

* Add a rough bench to test a finalizing a "long" chain

* Try to use complexity parameter for finality bench

* Improve long finality bench

* Remove stray dot file

* Remove old "worst" case bench

* Scribble some ideas down for pruning bench

* Prune headers during benchmarking

* Clean up some comments

* Make finality bench work for entire range of complexity parameter

* Place initialization code into a function

* Add bench for block finalization with caching

* First attempt at bench with receipts

* Try and trigger validator set change

* Perform a validator set change during benchmarking

* Move `validators_change_receipt()` to shared location

Allows unit tests and benchmarks to access the same helper function
and const

* Extract a test receipt root into a constant

* Clean up description of pruning bench

* Fix cache and pruning tests

* Remove unecessary `build_custom_header` usage

* Get rid of warnings

* Remove code duplication comment

I don't think its entirely worth it to split out so few lines of code.
The benches aren't particularly hard to read anyways.

* Increase the range of the complexity parameter

* Use dynamic number of receipts while benchmarking

As part of this change we have removed the hardcoded TEST_RECEIPT_ROOT
and instead chose to calculate the receipt root on the fly. This will
make tests and benches less fragile.

* Prune a dynamic number of headers

bridges/modules/ethereum/src/import.rs

@@ -163,7 +163,7 @@ mod tests {
 	use super::*;
 	use crate::mock::{
 		run_test, secret_to_address, test_aura_config, test_validators_config, validator, validators_addresses,
-		HeaderBuilder, KeepSomeHeadersBehindBest, TestRuntime, GAS_LIMIT,
+		validators_change_receipt, HeaderBuilder, KeepSomeHeadersBehindBest, TestRuntime, GAS_LIMIT,
 	};
 	use crate::validators::ValidatorsSource;
 	use crate::{BlocksToPrune, BridgeStorage, Headers, PruningRange};
@@ -316,9 +316,7 @@ mod tests {
 				&validators_config,
 				Some(101),
 				header11.clone(),
-				Some(vec![crate::validators::tests::validators_change_recept(
-					latest_block_id.hash,
-				)]),
+				Some(vec![validators_change_receipt(latest_block_id.hash)]),
 			)
 			.unwrap();
 			assert_eq!(finalized_blocks, vec![(parent_id, Some(100))],);