SMR-1834-WETH-Bridging

[proletesseract]

WETH bridging is now handled. WETH is unwrapped and send as ETH through the bridge.

Callouts

• Added interface for WETH for use in the bridge contracts
• Added contract for WETH (copied from the WIMX contract) for use in the test suite.
• Added receive() external payable {} method to root bridge so the WETH contract can send the ETH back which we unwrap.
• Unit and Integration tests added

[Benjimmutable]

Could we add the steps into ./deploy.sh that deploy WETH (if local), and instructions in README for how to trigger this local deployment of WETH, and explaining that it needs to be manually set iff ./deploy.sh is not going to be run with the local flag

[proletesseract]

I've addressed the feedback here.

• Fixed the nits
• Reorganised the root bridge contract to meet the layout guidelines linked
• Restructured the main if/else statement in the _deposit function to be a bit clearer on whats happening
• Removed the need to parse in the feeAmount
• Added a WETHDeposit event
• Removed the _depositWrappedETH function and simply called deposit after the unwrapping

One thing i was thinking is we could just put the deposit call at the end of the _unwrapETH function and remove the need to call it then _deposit. We don't have a use case for only unwrapping yet and it's a private function, so currently its technically more modular than it needs to be. Not sure it's a big deal, happy to leave it how it is unless any major objections.

[proletesseract]

the question i had above has been resolved and we decided to go with the option of combining the unwrapping and deposit steps into one function