contracts: Simplify benchmarks (#13595)

* Remove batching

* Benchmark in bytes not kilobytes

* ".git/.scripts/commands/bench/bench.sh" pallet dev pallet_contracts

* ".git/.scripts/commands/bench/bench.sh" pallet dev pallet_contracts

* ".git/.scripts/commands/bench/bench.sh" pallet dev pallet_contracts

* ".git/.scripts/commands/bench/bench.sh" pallet dev pallet_contracts

* Add rationale for picking batch numbers

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Co-authored-by: command-bot <>