Implement tryCalcRate, implement new precision.

[Brean0]

Problem

When MultiFlowPump attempts to Cap the change in ratio of reserves, It calls WellFunction.calcRate(..) in order to calculate the last rate with the last reserves, and the current rate. If calcRate fails, then the Pump reverts, and thus bricks the Well.

When MultiFlowPump attempts to calculate the Capped Reserves, it assumes the Well uses a Constant Product 2 Well Function.

Solution

• Update MultiFlowPump to fail gracefully when calcRate fails.

• Update IMultiFlowWellFunction to implement ratioPrecision(uint256 j, bytes data), which returns the precision that the MultiFlowPump should use when calculating the capped Reserves.

• Update MultiFlowPump to use ratioPrecision when calculating for ratios[j] in calcReservesAtRatioSwap.

• Update ConstantProduct2, ConstantProduct, and Stable2 to implement ratioPrecision.

• Update IWellFunction to implement version(), allowing users to verify WellFunctions.