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Gas token solution submission (#1045)

This PR adds a wrapper contract around solution submissions that allows burning an appropriate amount of [gas tokens](https://1inch-exchange.medium.com/1inch-introduces-chi-gastoken-d0bd5bb0f92b) to offset the cost of settling an auction.

It's using the same signature for settlement as batch exchange but wraps the call into a modifier taken from the block article above (slightly adjusted to not use `freeFrom` as this is more expensive than if the wrapping contract actually had gas token balance).

It allows setting a threshold below which gas tokens would not be used (as it might not be worth burning tokens in times of loww gas prices)

In order to allow future withdrawl of fee rewards, it also exposes an "execute" method that can make arbitrary calls by the owner (by default the account deploying the contract). Submit solution itself is called permissionlessly by any account.

### Test Plan

Unit tests, once reviewed I will deploy on mainnet and run some "simulations" on how previous solution submissions would have performed before making the solver point at this contract instead of the real exchange.

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