Feat: Reintroduce segmented fees - #455

• reintroduces the concept of fee segmentation if invariant should be pushed > 0 in a swap
• removes the priorityFee, pool controller no longer pays a priority fee but is still able to update params

The fact that the invariant was being pushed > 0 was almost certainly the root cause of the contracts breaking. By bounding the invariant you can insure that you will not reach the boundaries of the ppf (0, 1).

* k = Φ⁻¹(y/K) - Φ⁻¹(1-x) + σ√τ
* y = KΦ(Φ⁻¹(1-x) - σ√τ + k)
* x = 1 - Φ(Φ⁻¹(y/K) + σ√τ - k)

Note that in the above invariant the y reserve increases along with K leading to a scenario where the curve is trivially pushed to Φ⁻¹(y/K) where y > K thus breaching the ppf bounds.