S2 upgr well remediations 2

[Brean0]

This PR addresses the findings found from the codeArena remediation audit.

• decreased PRICE_THRESHOLD from 100 to 10, used in calcReservesAtRatioSwap and calcReserveAtRatioLiquidity. This significantly increases the accuracy of the reserve with a marginal increase in gas.
• In extreme edge cases, calcLpTokenSupply would not converge at extreme ratios, and would instead oscillate +/- 2 unit around the target value. An boolean check was added if this case occurred, which stops the infinite loop and return the average.
• Stable2 currently sets the initial step size and reserves by checking the absolute difference between the target price and the high/low price from the lookup table. This results in cases where the price may be marginally closer to the target price, but in practice, the reserves are much further from the target reserves (which is most obvious in the extreme range case). This caused the newton estimation to iterate through many more times than expected. Stable2 now checks the percent difference instead, which is a much more precise check to set the guess.