PriceAuthority doesn't allow AMM to modify amountIn when submitting prices

[Chris-Hibbert]

Describe the bug

The PriceAuthority presumes that prices provided by calcAmountIn and calcAmountOut will only provide one amount. Autoswap's getOutputForGivenInput() will sometimes update the amountIn as well as providing the amountOut, and conversely for getInputForGivenOutput().

Expected behavior

The PriceAuthority should transmit the best price information available.

Additional context

In priceAuthority.js, trigger expects that calcAmountOut will only produce amountOut. This forces the priceAuthority in the AMM to discard its amountIn before responding. The current version of getOutputForGivenInput() in autoswap returns the amountOut along with a possibly updated amountIn.

quoteGiven and quoteAtTime should take both values from calcAmountOut, and quoteWanted should take both values from calcAmountIn.

[Tartuffo]

@samsiegart to make sure we are displaying the answer consistently.

[Tartuffo]

@dtribble Is this a "nice to have" for MN-1?

[Tartuffo]

This can be done as part of the major work on PricingAuthority, #2688. Implementing this issue later should not break anything.