Replace assert with require or custom error

[Alexangelj]

DFMM/src/ConstantSum/ConstantSum.sol

Line 112 in e64e222

assert(liquidityDelta >= int256(minLiquidityDelta));

Assertions don't provide the best feedback for errors since they use generic messages that can be triggered in other scenarios - we should use a require statement or custom error with a unique message/error for this case.

[clemlak]

I think this contract is mostly used by @Autoparallel for testing purposes, we're not sure if we'll actually release it.

[clemlak]

Closed by #53.