test(verify): cover blockscout verifier with etherscan api key set on unknown chain

[Osraka]

Motivation

Adds regression coverage for the forge verify-contract verifier routing case from #11430. The existing test covers an unknown Etherscan chain with Blockscout and --verifier-url; this adds the same path with ETHERSCAN_API_KEY set so the explicit Blockscout verifier continues to avoid Etherscan API URL resolution.

Solution

Extend the existing can_validate_verifier_settings test with the exact combination:

• unknown Etherscan chain resolved from the Lisk Sepolia RPC
• --verifier blockscout
• explicit --verifier-url
• ETHERSCAN_API_KEY present in the command environment

The expected result remains the Blockscout already-verified flow, not No known Etherscan API URL.

Validation

• cargo test -p forge --test cli can_validate_verifier_settings
• cargo test -p forge --test cli verify::

Note: cargo test -p forge --test verify is not a valid target in this repo; these verify tests live under the cli integration test target.