Add para pallets to polkadot benchmarks (#4045)

* Add para pallets to polkadot benchmarks

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

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

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

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