fix: add missing benchmark for transfer_assets

[ipapandinas]

Pull Request Summary

Closes #1677

This PR implements the missing set_up_complex_asset_transfer helper in all three runtimes so transfer_assets gets a real weight.

[ipapandinas]

/bench astar,shibuya,shiden pallet_xcm

[github-actions]

Benchmarks job is scheduled at https://github.com/AstarNetwork/Astar/actions/runs/31189950688.
Please wait for a while.
Branch: fix/asset-transfer-benchmark
SHA: a88869d

[github-actions]

Benchmarks have been finished.
You can download artifacts if exists https://github.com/AstarNetwork/Astar/actions/runs/31189950688.

[github-actions]

Package	Line Rate	Branch Rate	Health
pallets/dynamic-evm-base-fee/src	84%	0%	✔
pallets/astar-xcm-benchmarks/src	86%	0%	✔
precompiles/dispatch-lockdrop/src	89%	0%	✔
precompiles/sr25519/src	69%	0%	➖
precompiles/xcm/src	70%	0%	➖
primitives/src/xcm	66%	0%	➖
pallets/inflation/src	58%	0%	➖
primitives/src	44%	0%	❌
pallets/astar-xcm-benchmarks/src/generic	100%	0%	✔
pallets/dapp-staking/src/test	0%	0%	❌
precompiles/dapp-staking/src/test	0%	0%	❌
pallets/collective-proxy/src	94%	0%	✔
pallets/collator-selection/src	82%	0%	✔
pallets/dapp-staking/src/benchmarking	94%	0%	✔
pallets/dapp-staking/src	83%	0%	✔
pallets/dapp-staking/rpc/runtime-api/src	0%	0%	❌
pallets/astar-xcm-benchmarks/src/fungible	100%	0%	✔
pallets/democracy-mbm/src	30%	0%	❌
precompiles/substrate-ecdsa/src	74%	0%	➖
pallets/vesting-mbm/src	87%	0%	✔
precompiles/assets-erc20/src	77%	0%	➖
pallets/xc-asset-config/src	57%	0%	➖
precompiles/dapp-staking/src	89%	0%	✔
Summary	73% (3469 / 4721)	0% (0 / 0)	➖

Minimum allowed line rate is 50%