Add tx-cost-diff executable #6048

Job	Run time
nix flake check	8s
Benchmarks (hydra-node, tx-cost, --output-directory $(pwd)/../benchmarks)	10s
Build haddock using nix	9s
Build & test (plutus-cbor)	1s
Build & test (plutus-merkle-tree)	1s
Build & test (hydra-plutus)	1s
Build specification using nix	11s
Build & test (hydra-tui)	1s
Benchmarks (hydra-node, micro, -o $(pwd)/../benchmarks/ledger-bench.html)	9s
Benchmarks (hydra-cluster, bench-e2e, datasets datasets/1-node.json datasets/3-nodes.json --outpu...	10s
Build & test (hydra-node)	8s
Compute cost differences	12s
Benchmarks (plutus-merkle-tree, on-chain-cost, $(pwd)/../benchmarks)	10s
Build & test (hydra-tx)	1s
Build & test (hydra-cluster)	8s
Publish test results	1s
Documentation	1s
Publish benchmark results	1s
	1m 43s

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