Add PerpV2 test fixture

[cgewecke]

Adapts PerpV2's ClearingHouse test fixture for set-protocol-v2

Some differences:

• using uniswapV3 sdk (and JSBI) to encode the square root price for the vAMM
• replace smocked chainlink aggregator with ChainlinkAggregatorMock contract
  • we can't use smock because it only works with the in-process hardhat network
  • we use localhost / may want to run our tests on arbitrum testnet at some point because its architecture is substantially different than ethereum-evm (despite their compatibility)
• have namespaced the external Perp ABIs to avoid conflicts in the typechain folder with other protocols (for example, both PerpV2 and Yearn have an ABI for Vault)

TODO

• Encode network gas in ABI (super slow w/ estimation atm)
  • Hook in this typechain subtask