parachains: Fix configuration module (#4540)

* parachains: Fix configuration module

Closes #4529
Closes #4533

I figured that trying to avoid updates does not really worth it to keep.
This is because we seem to not update the configuration often and when
we do we approach this carefully. Thus possibility of a redundant update
is really negligable. At the same time, if such a redundant update does
happen then the effects of that are really small: just some wasted
storage interactions.

On the other hand, making it work was a little bit annoying. With the
proper fix for the pending updates this would be even more annoying
since now we would have to add combinatorically more cases to test this.

So I figured that I will just scrap that and simplify the code.

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

* 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=westend-dev --steps=50 --repeat=20 --pallet=runtime_parachains::configuration --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --header=./file_header.txt --output=./runtime/westend/src/weights/runtime_parachains_configuration.rs

* review fixes

Co-authored-by: Parity Bot <[email protected]>