[stableswap]: Prevent int overflows in intermediate CFMM calculations

[AlpinYukseloglu]

Background

Our CFMM solvers (even the simplified ones) have extremely large terms (^8) in them that cause int overflows for relatively small pools. It likely isn't possible to simplify the solvers much further in a way that would bound the largest term, so we will have to find another way to deal with extremely large intermediate terms.

Suggested Design

Some options might be:

• Find a way to shift around terms such that the largest one is always bounded
• Add a switch that, for very large inputs, removes extremely small terms to simplify logic and minimize large exponents

Acceptance Criteria

• A stableswap pool with $100M in each asset should not overflow

[AlpinYukseloglu]

Looks like we might be able to bound the largest term (x^8 and k^2) like this:

Will continue trying to wrangle this to fit inside bounds but this overflow issue is looking more and more solvable

[AlpinYukseloglu]

Closed by #2777 and #2778