UMIP 40 -Add BTC-BASIS-3M/USDC, BTC-BASIS-6M/USDC, ETH-BASIS-3M/USDC, ETH-BASIS-6M/USDC as price identifiers

The DVM should support price requests for both BTC-BASIS-3M/USDC, BTC-BASIS-6M/USDC, ETH-BASIS-3M/USDC, ETH-BASIS-6M/USDC price indices. BTC-BASIS-3M/USDC is defined as: min(max(100.0 * [1 + (F-S)/S], 75.0), 125.0), where F references a basket of BTC futures that are set to expire in March and S represents a basket of BTC spot prices. ETH-BASIS-3M/USDC is defined in the same way, except the F and S correspond to ETH futures and spot. Similarly, the 6M BTC and ETH price identifiers would be the same formula except with futures that are set to expire in June instead of March .