Set CurrentCodeHash before running some dispatchable benchmarks (#4645)

* Set CurrentCodeHash before running some dispatchable benchmarks

* Use insert instead of put

* Actually hash the ValidationCode

* cargo run --quiet --release --features=runtime-benchmarks -- benchmark --chain=westend-dev --steps=50 --repeat=20 --pallet=runtime_parachains::paras --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --header=./file_header.txt --output=./runtime/westend/src/weights/runtime_parachains_paras.rs

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