Allow nomination pools to chill + fix dismantle scenario (#11426)

* make pool roles optional

* undo lock file changes?

* add migration

* add the ability for pools to chill themselves

* boilerplate of tests

* somewhat stable, but I think I found another bug as well

* Fix it all

* Add more more sophisticated test + capture one more bug.

* Update frame/staking/src/lib.rs

* reduce the diff a little bit

* add some test for the slashing bug

* cleanup

* fix lock file?

* Fix

* fmt

* Update frame/nomination-pools/src/lib.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Update frame/nomination-pools/src/lib.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Update frame/nomination-pools/src/lib.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Update frame/nomination-pools/src/mock.rs

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Fix build

* fix some fishy tests..

* add one last integrity check for MinCreateBond

* remove bad assertion -- needs to be dealt with later

* nits

* fix tests and add benchmarks for chill

* remove stuff

* fix benchmarks

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

* remove defensive

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Parity Bot <admin@parity.io>