Mainnet WETH Deployment

[jflatow]

~~WIP~~ Ready for review now.

Changes made in preparation for launching a ~~mainnet/ETH~~mainnet/WETH deployment.

• adds mainnet-weth scenario base
• adds configuration for mainnet/weth deploy with wstETH and cbETH as collateral assets
• adds a WstETHPriceFeed.sol contract that calculates the wstETH / USD price using the stETH / USD price feed and the value of wstETH:stETH
• updates scenarios to work with ETH-based markets, where possible
• adds a matchesDeployment filter to allow for scenarios that specifically target (or avoid) the mainnet-weth deploy
• adds a getRewardToken fn to context, to allow retrieving the reward token even when it is not a collateral asset

Remaining todos before we can launch:

• [x] set the supply caps back to 0
• [x] replace the cbETH price feed with the actual Chainlink cbETH / USD price feed (when it's available)
• [x] decide on actual configuration params
• [ ] get OZ audit on WstETHPriceFeed.sol
• [ ] launch a new version of the Liquidator Bot for mainnet/eth
• [x] deploy new Bulker (#611)

[jflatow]

For setting the supply caps from 0, we need a separate migration w/ a proposal. For USDC we also seeded reserves, not sure if we want to try to do that here. Doing rewards after I think makes sense

[jflatow]

• [x] We also need to make the name consistent everywhere (cWETHv3)