Etherscan --> Blockscout migration

[fainashalts]

We are migrating to Blockscout for OP Mainnet and OP Sepolia. It appears that this repo currently uses Etherscan for these networks.

This issue is primarily to find every OPM or OP Sepolia reference to Etherscan, replacing with Blockscout. We should also make sure any contracts we are relying on are already verified on Blockscout.

The new urls for OPM and Sepolia are https://explorer.optimism.io and testnet-explorer.optimism.io

[krofax]

@fainashalts This pr addresses this.
Waiting for reviews and approval. cc @bradleycamacho

[fainashalts]

@krofax awesome thank you! Feel free to close this once that is merged. 👍

[bradleycamacho]

Approved!