Support blockscout

[fainashalts]

PR description

This PR introduces blockscout support to Truffle's source-fetcher and fetch-and-compile functionality. In tandem with Ganache forking of the ConsenSys zkEVM, this support should allow for local debugging of transactions retrieved from the blockscout explorer.

Testing instructions

To test this PR, fork ganache using the ConsenSys zkEVM testnet (this is only available on blockscout's explorer but you could also use mainnet or goerli if you use a verified contract that isn't also verified on etherscan or sourcify, I suppose). Attempt to debug a transaction you find on blockscout.

Documentation

• [ x] I thought about documentation and added the doc-change-required label to this PR if documentation updates are required.

Breaking changes and new features

• [ x] I have added any needed breaking-change and new-feature labels for the appropriate packages.

** This PR is still a work in progress **

To Do

• Determine whether fetching via other means (multi-file, json input) is necessary or if single file is sufficient
• Add multi-source tests if needed
• Add vyper test, to ensure processVyperResult works correctly
• Ensure handling of libraries is correct; ensure that processLibraries can return the appropriate information gleaned from blockscout's response
• Ensure constructor arguments are handled correctly
• Currently defaults to 200 runs, make sure that doesn't mess with bytecode
• Determine whether the optimization defaults are still an issue for contracts below Solidity 0.8.6

[haltman-at]

Closing this for the reasons discussed on #5935.