Generate Unit Tests for Benchmarks (#5527)

* Update to latest staking

* generate tests for benchmarking

* add tests, fix warnings

* starting on democracy

* impl_benchmark_tests

* Way more readable

* add test feature flag (does this work?)

* Fix `successful_origin` impl

* democracry benchmark tests

* Fix example benchmarks, add tests

* identity benchmark tests

* Update im-online benchmark tests

* try to add session benchmarking tests (problem with mock)

* staking and timestamp

* add test for treasury, issue with dynamic contains

* utility

* Vesting

* test instead of check

* hide until we figure out what is wrong

* add docs

* close code

* Create custom mock for session-pallet-benchmarking

* Use refcell pattern

* make un-pub

* test-linux-stable includes `runtime-benchmarks` feature

* Revert "test-linux-stable includes `runtime-benchmarks` feature"

This reverts commit a2dab38abd18ac3eb8a6220e4a00e687740bd38c.

* run tests in `--release`

* undo balance change

* build wasm

substrate/primitives/state-machine/src/in_memory_backend.rs

@@ -364,6 +364,10 @@ impl<H: Hasher> Backend<H> for InMemory<H> where H::Out: Codec {
 	fn usage_info(&self) -> UsageInfo {
 		UsageInfo::empty()
 	}
+
+	fn wipe(&self) -> Result<(), Self::Error> {
+		Ok(())
+	}
 }
 
 #[cfg(test)]