feat: solvers - consume full swap amount

[parketh]

Summary

This PR updates the swap amount calculation logic in swap_lib to better handle rounding errors when calculating swap amounts.

Description

As part of the reintegration of Solvers with AVNU, their team identified that in some exact in swaps, the amount actually consumed is lower than the amount requested even though liquidity is enough to fill the swap.

This happens because we calculate the net swap amount based on available liquidity, and add back fees using the net_to_fee util function. This leads to rounding errors in some cases, where the actual amount consumed deviates +/- 1 from the requested swap amount.

This PR adds a fix to consume the full swap amount for exact in swaps that that are fully filled over non-zero liquidity.

Testing

snforge test --max-n-steps 4294967295