Safety feature: allow swap is USDC de-pegs again

[alexsanya]

Changes:

• add swapCollateral to swap locked in contract USDC to another stable coin in case USDC loses it's peg again
• winner should run transaction to claim tokens - this will allow to get any token locked in contract
• integration with Uniswap V3
• added mocks for Chainlink price feeds in tests
• emit events on start and settle - signals for the bot

Workflow:

• Bot will deploy smart contract
• Parties will deposit their assets and the bet is started
• Once the bet is started the bot will check USDC price every 5 seconds and if it drops below threshold it will start to search the best swap route by looking at other stable-coins performance, available pools, fees and liquidity in Uniswap and once the route for conversion with minimal losses will be found the transaction will to be submitted
• If there is not enough liquidity in pools the partial swap will be performed and search continues
• When the bet is settled winner will get all the assets

Notes:

• Swap is only allowed by contract owner when the bet is started, USDC price is lower than threshold and output token is one of: USDT, BUSD, USDP, DAI
• settle only defines the winner and then winner should run transaction to claim each token locked in contract
• added Chainlink feed for USDC price