Audit fix: CGT vs Lockbox.

[Mc01]

Fixes [M-01] OptimismPortal2#finalizeWithdrawalTransactionExternalProof - ETHLockbox Misaccounting With Custom Gas Token Withdrawals

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Note

Medium Risk
Touches core deposit/withdrawal execution paths and configuration gating; mistakes could change lock/unlock behavior or break networks that rely on the lockbox feature.

Overview
Prevents ETHLockbox from being used on custom-gas-token (CGT) chains to avoid incorrect ETH accounting during deposits/withdrawals.

OptimismPortal2 now treats lockbox as active only when the gas-paying token is Constants.ETHER, SystemConfig.setFeature rejects enabling Features.ETH_LOCKBOX on CGT chains, and OPContractsManagerStandardValidator adds corresponding validation (including asserting lockbox incompatibility with CGT). New tests cover the feature-flag revert and that deposits on CGT chains never call ethLockbox.lockETH even if the flag/storage are force-enabled.

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