Remix Plugin Lookup on Etherscan shows "Not Verified" instead of API key error

[kuzdogan]

When querying the Etherscan API with a wrong API key the Lookup shows "not verified" instead of an API error.

To reproduce:

• Enter an invalid Etherscan key for Etherem Mainnet
• Lookup 0x1F98431c8aD98523631AE4a59f267346ea31F984

In general I think we should let the user see the API response, but also handle this case specifically.

[manuelwedler]

done, ethereum/remix-project#6225 was merged