feat(BASE-104): add support for L3 withdrawals requiring instant finality

[robriks]

Introduces utilities targeting instantaneous TEE-trusted finality, aligned with l3 changes added for base/base and base/contracts

Addresses BASE-104

Note on limitations

This repository currently only provides withdrawal capabilities on a manual, per-user basis (to exit Base to Ethereum). This PR in turn adds the bare minimum to add support for instant finality L3s, also on a manual per-user basis. Future work should investigate a way to extend the functionality introduced in this PR to run as an automated service, detecting withdrawals signaled on the L2 and automatically relaying + settling them on the L3. I suggest we reuse the code already built in this branch, adding serve subcommand to the base/withdrawer CLI that runs as a long-lived daemon to deliver a fully automated withdrawal experience for chains with TEE-backed instant finality.

Summary

Adds --instant-finality CLI flag that enables single-transaction withdrawal proving and finalization for L3 appchains with TEE-backed immediate finality. This calls proveAndFinalizeWithdrawalTransaction on OptimismPortal2 instead of the separate prove → wait → finalize flow.

• New --instant-finality flag (implies --fault-proofs)
• Reuses existing proof parameter generation, gas handling, dry-run, and confirmation patterns
• No behavioral changes when the flag is not set

Context

Companion to the contract changes in base/contracts (l3-changes branch) which introduce proveAndFinalizeWithdrawalTransaction on OptimismPortal2 for chains where PROOF_MATURITY_DELAY_SECONDS == 0 and disputeGameFinalityDelaySeconds == 0 (changes in base/base).

[linear]

BASE-104