Benchmarks for offences pallet. (#5851)

* really rough mock runtime

* start to work on offences

* Make sure to start the session.

* Update to latest master.

* Add verify.

* Fix on_initialize benchmark.

* Add grandpa offence.

* Add Babe offence benchmarking.

* Enable babe test.

* Address review grumbles.

* Address review grumbles.

* Address review grumbles part 1/2

* use currency trait

* features

* Check events explicitly.

* Auto-impl tuple converter.

* Removed dead code.

* add test feature flag

* dont use std

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/Cargo.lock

@@ -4393,11 +4393,18 @@ dependencies = [
  "frame-benchmarking",
  "frame-support",
  "frame-system",
+ "pallet-babe",
+ "pallet-balances",
+ "pallet-grandpa",
  "pallet-im-online",
  "pallet-offences",
  "pallet-session",
  "pallet-staking",
+ "pallet-staking-reward-curve",
+ "pallet-timestamp",
  "parity-scale-codec",
+ "serde",
+ "sp-core",
  "sp-io",
  "sp-runtime",
  "sp-staking",