feat: add metis support

[sakulstra]

Motivation

I wanted to use erhers-rs for Metis network

Solution

Add ing Metis in this pr

Following the example here: https://github.com/gakonst/ethers-rs/pull/2316/files

[mattsse]

lgtm

[prestwich]

CI failures unrelated. Please rebase and resolve conflicts, then we can merge

[sakulstra]

@prestwich rebased.

When looking into metis/blockscout also noticed that some foundry commands don't work with blockscout, although blockscout claims to be etherscan compatible: foundry-rs/foundry#4776 - not quite sure where to fix this. As i understand the contract.rs is already more or less agnostic, but probably some adjustment is needed here: https://github.com/gakonst/ethers-rs/blob/master/ethers-etherscan/src/lib.rs#L78 as on blockscout there are no api keys?

[prestwich]

please run cargo +nightly fmt and commit the results :) The clippy CI failure may be unrelated. looking into it

When looking into metis/blockscout also noticed that some foundry commands don't work with blockscout, although blockscout claims to be etherscan compatible: foundry-rs/foundry#4776 - not quite sure where to fix this. As i understand the contract.rs is already more or less agnostic, but probably some adjustment is needed here: https://github.com/gakonst/ethers-rs/blob/master/ethers-etherscan/src/lib.rs#L78 as on blockscout there are no api keys?

I'm not sure as i don't really follow blockscout closely. This is at the very least worth a new issue