Companion for substrate/pull/7161 (#1739)

* Companion for https://github.com/paritytech/substrate/pull/7161

* Update weights

* Update tests

* remove weight tests

* Update weights using benchmarking machine

./substrate2/target/release/substrate benchmark --chain dev --steps 50 --repeat 20 --pallet pallet_elections_phragmen --extrinsic "*" --raw --execution=wasm --wasm-execution=compiled --output

* "Update Substrate"

Co-authored-by: Shawn Tabrizi <[email protected]>
Co-authored-by: parity-processbot <>