feat(multicall): enable multicall response as Vec if all return types are the same

[rymnc]

No description provided.

[cursor]

PR Summary

Adds multicall simulation API simulate_vec (with get_response_vec) to return a Vec<T> when all call return types are the same, plus an e2e test; minor formatting tweak in retryable client.

• Multicall API (programs):
  • Add CallHandler<Vec<ContractCall>, ()>::simulate_vec<T>() to simulate multicalls and return CallResponse<Vec<T>> when all calls share the same return type.
  • Add helper get_response_vec<T>() to parse receipts into a homogeneous Vec<T>.
• E2E Tests:
  • Add test_multi_call_simulate_vec in e2e/tests/contracts.rs validating simulate_vec returning Vec<u64> across three calls.
• Provider:
  • Minor formatting of RetryableClient::connect_with_fallbacks signature in packages/fuels-accounts/src/provider/retryable_client.rs.

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