feat: Flashloan support

[MartinquaXD]

Problem

We want to allow solvers and users to make use of flashloans for settling orders. For context a flashloan is a mechanism where an actor requests some amount of tokens, is allowed to use them within the same transaction and has to pay them back in full (sometimes plus interest) at the end of the transaction. If the flashloan lender does not get back the expected amount in tokens the whole transaction will revert and no balances will have changed.
This feature would enable solvers to handle liquidations for bigger amount than they can bankroll themselves.

The overall plan is to let users provide "hints" in their order appdata that it may need to be settled using a flashloan (and some details around that). The driver will read this information and let the solver know about it (flashloans introduce gas overhead that the solver should be aware for when computing fees) and will encode the transaction appropriately (using a helper contract that still needs to be developed).
Finally the post processing step where we index and analyze Settlement events needs to be made compatible with a smart contract calling the settle() function of the settlement contract.

Details to the individual steps can be found in the linked issues.
In order to ensure that tasks don't depend on each other let's introduce some interface which we code against. Those can then be used with Default implementations until we actually have the real data.

Implementation Plan

• Make settlement indexing compatible with smart contract solvers #3177
  • the issues outlines an e2e testing plan that is quite involved. Alternatively this e2e test could be delayed until the end to get 1 e2e test that covers the whole feature.
• propagate flashloan hints
  • Accept flashloan hints during order creation #3214
  • driver fetches flashloan hints for orders #3215
  • driver informs solver about flashloan hints #3216
• encode flashloan transaction (depend on helper contract)
  • generate contract bindings for flashloan helper #3217
  • encode flashloan call in the driver #3218
• flashloan e2e test #3219