fuzz test pool library for solvency

[moodysalem]

this should be much easier to do now that pool logic is in a library. verify that via calls to modify position and swap, all positions will always be solvent. ~~we should probably use mythx for this. tried it with forge, but it has some drawbacks over echidna/mythx style fuzz tests, mainly does not test sequences of transactions, but handling reverts is also painful~~ https://github.com/Uniswap/core-next/commit/b18e172a151e9c6e7c22a63011bc048a2e393790

[marktoda]

I have an idea for how to do this with forge - giving it a shot

[hensha256]

@marktoda to redo this with invariant tests