Make election benchmarks more *memory-aware* (#9286)

* Make benchmarks a bit better with mem

* Make election benchmarks more *memory-aware*

* Fix a few errors

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

* Manually fix the weights

* Update lock file

* remove dupe

* Fix tests

* cargo update pwasm

Co-authored-by: Parity Bot <admin@parity.io>