Fix/controller swap fees

[clemlak]

Cf https://github.com/cantinasec/review-primitive-excalibur/pull/1#discussion_r1528840907

[Alexangelj]

Let's use mulWadUp, which will only make fees == 0 when deltaLiquidity == 0, then we can just try to avoid deltaLiquidity == 0 in the other parts of the code to avoid the fees == 0 code branch

[kinrezC]

Also, should we be checking if controllerFee > 0 in the if?

[kinrezC]

Maybe there's a case where you want to burn liquidity (dumb idea ik), in which case you might want non-zero controllerFee but feeCollector == address(0)?

[clemlak]

Maybe there's a case where you want to burn liquidity (dumb idea ik), in which case you might want non-zero controllerFee but feeCollector == address(0)?

Yeah, I think it makes sense to check the controller fee in the if condition instead of the address.

[clemlak]

If we want to prevent swap from burning liquidity we can still reintroduce the address check later.