Add Control to Growth of the Staking Pallet (#8920)

* start count

* track count

* add max limit

* min bonds for participating

* respect min bond when unbonding

* revert a bit of u32

* fix merge

* more merge fixes

* update to `Current*`

* add helper functions

* Update frame/staking/src/lib.rs

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

* fix

* minbond as storage

* checkpoint

* chill_other

* better bond tracking

* MinBond to MinNominatorBond

* better doc

* use helper function

* oops

* simple hard limits to validators / nominators.

* better doc

* update storage version

* fix tests

* enable migrations

* min bond tests

* chill other tests

* tests for max cap

* check `None` on cap too

* benchmarks

* Update frame/staking/src/lib.rs

* Update frame/staking/src/lib.rs

Co-authored-by: Zeke Mostov <32168567+emostov@users.noreply.github.com>

* Update frame/staking/src/lib.rs

Co-authored-by: Zeke Mostov <32168567+emostov@users.noreply.github.com>

* Update frame/staking/src/tests.rs

Co-authored-by: Zeke Mostov <32168567+emostov@users.noreply.github.com>

* fix benchmark

* cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* nits

* fix reap_stash benchmark

* remove lower bound to min bond

Co-authored-by: kianenigma <kian@parity.io>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Parity Bot <admin@parity.io>
Co-authored-by: Zeke Mostov <32168567+emostov@users.noreply.github.com>

substrate/frame/staking/src/testing_utils.rs

@@ -30,7 +30,9 @@ const SEED: u32 = 0;
 /// This function removes all validators and nominators from storage.
 pub fn clear_validators_and_nominators<T: Config>() {
 	Validators::<T>::remove_all(None);
+	CurrentValidatorsCount::<T>::kill();
 	Nominators::<T>::remove_all(None);
+	CurrentNominatorsCount::<T>::kill();
 }
 
 /// Grab a funded user.