WeightedPool simulator

[EndymionJkb]

Written to investigate the behavior of extreme swap fees, the infrastructure created for the fee simulation could be reused for other purposes. (In any case I didn't want to lose it.)

This was written before the Python simulation tools being developed by Integrations, but having a "native" TS way to do this right in the repo might be useful as well. You can create a WeightedPool with arbitrary tokens and weights, and "seed" it with a given set of prices and desired total dollar amount of liquidity, so that the starting balances will be realistic.

This could be used to write new benchmark tests.