Benchmark Staking and Session Pallet (#5183)

* starting bench

* More

* more

* Payout Validator

* Give each validator exactly n nominators

* Update with test

* Try to add accounts to chain spec

* Undo changes to chainspec

* Payout nominator

* Rebond and Reap Stash

* Set history depth

* fix smelly code

* cancel deferred slash

* new_era bench

* do_slash benchmark

* Add features

* undo extrinsic move

* lower

* Update new era

* Update benchmarking.rs

* whitespace

* Apply suggestions from code review

Co-Authored-By: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* fixes

* nit

* Refactor tests, initial code

* Move session benchmarks to avoid cyclic deps

* Update lib.rs

* Fix warnings

* Move impl

* Update to do random nominator allocation

* add feature to benchmark pallet

* Remove extra stuff

* Update based on feedback

* Less intrusive

* Remove `transfer_idle_users`

* remove again

* unused dep

* test feature flag

* Update to latest substrate

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

substrate/frame/benchmark/src/lib.rs

@@ -26,6 +26,7 @@ use frame_system::{self as system, ensure_signed};
 use codec::{Encode, Decode};
 use sp_std::prelude::Vec;
 
+#[cfg(feature = "runtime-benchmarks")]
 pub mod benchmarking;
 
 /// Type alias for currency balance.