feat(swap): support swapping through WVET

[OliverNChalk]

Background

Previously we had routing issues with the Uniswap multi hop router. To address this we disabled multihop routing, forcing direct routing for all swaps. This means that if there exists an illquid pool for your swap, you trade will be fulfilled by that pool - even if a better swap exists.

This means the user is responsible for always swapping to VET first (if you're swapping two non-VET assets). One way to improve the current situation is to ignore non VET pools and force all routes to go through VET. This would e.g. mean that VEX-veUSD gets expended to VEX-->VET-->veUSD.

Details

Currently, on Vexchange all major pairs are in the form of TOKEN<>WVET. For this reason, we should be swapping exclusively through pairs that have WVET as one of the assets. Currently, the UI will simply load the pair the user has provided. So if the user attempts to trade VEX<>veUSD they will get rekt. To solve this, we should apply this simple algorithm to determine the optimal route:

IF TOKEN_IN == WVET || TOKEN_OUT == WVET
    ROUTE = [TOKEN_IN, TOKEN_OUT]
ELSE
    ROUTE = [TOKEN_IN, WVET, TOKEN_OUT]
END ELSE

IF IS_VALID_ROUTE(ROUTE)
    ROUTER.SWAP(ROUTE)
ELSE
    WARN_USER()
END ELSE

VALID_ROUTE() checks that each hop goes through a valid pair, e.g. in the case the user is not trading WVET, then it must check that TOKEN_IN<>WVET AND TOKEN_OUT<>WVET exist.

Deliverables

• Feasibility evaluation of proposed algorithm (present at standup for approval)
• Implementation of propose algorithm
• Deletion of dead/unnecessary code
• Extensive testing of implemetnation