Add initial optimism deps and contracts

[cgewecke]

DO NOT MERGE: PR TARGETS #81

PR:

• selects the initial set of core contracts and test contract deps for Optimism L2
• adds optimism's hardhat plugin and hardhat sizer dependencies (b/c size limits are critical)
• add two OpenZeppelin contracts modified to be ovm-compatible:
  • SafeERC20.sol
  • Address.sol
• adds misc. scripts to get everything running.
• minimizes the circleci config to build. We will need to add custom setup as it becomes available. Some things like coverage are not currently possible with an OVM client.

Additional notes

The new Zeppelin contracts are ported from derekbar90/optimism-openzeppelin-compat. Optimism does not support the BALANCE opcode. Instead balances are checked by querying an address's native WETH balance on the Optimism network. These contracts are updated to reflect that.

Optimism:

• Their hardhat compiler plugin has a bug I've written a patch for here and reported at eth-optimism/optimism 64.
• The compiler substantially increases the size of contracts (network size constraints are the same as Mainnet: ~24kb)
• The OVM has a lower gas limit (9_000_000) and large deployments can easily burn through it because the OVM runs additional logic in contract constructors to verify that no illegal opcodes are in the contract bytecode.

The initial contract set is below. Work to get everything structured so that it will deploy is ongoing.

Contracts	Deploys to L2	Notes
Controller	Yes
IntegrationRegistry	Yes
PriceOracle	Yes
SetToken	Yes	Restructuring WIP
SetTokenCreator	No	Size limit must be < 22.57 to avoid OOG
SetValuer	WIP	Probably ok
BasicIssuance	WIP	Probably ok
StreamingFeeModule	WIP	Probably ok
TradeModule	WIP	Probably ok

[gakonst]

The latest one is @eth-optimism/hardhat-ovm: https://www.npmjs.com/package/@eth-optimism/hardhat-ovm

[gakonst]

Should not be needed if you use hardhat-ovm

[cgewecke]

This project consumes its bytecode out of typechain factories rather than hardhat artifacts. The typechain plugin reads paths.artifacts here.

Note to self: check what this value is in the typechain plugin compile hook.

cache definitely removable.

[cgewecke]

Closing for the moment, will revisit when support for Optimism is scheduled