[HGP-38] Epoch 4 DEX Connectors Poll

A quarterly poll that places decentralized exchange connectors into Gold, Silver and Bronze tiers, which define the level of maintenance that the Foundation spends on each connector.

The choices for this poll are the current decentralized exchanges which have Gateway connectors (https://docs.hummingbot.org/gateway/) or the main Hummingbot client codebase like dYdX and Loopring.

DEXs with instances on different chains are considered a single exchange similar to CEX Connectors, this poll selects Gold (top 1), Silver (top 2-4), and Bronze DEXs based on voting power received.

The Foundation will treat the Gold DEX Connector as the "gold standard" and map all of its swap and liquidity provision endpoints and support instances on all major chains. For the Silver DEXs, we will utilize HBOT developer bounties to fund improvements and fixes.

The Foundation supports Gold and Silver DEXs by running long-term testing bots for their connectors and providing HBOT rewards to users who answer community questions related to them.

Any other DEX that meets the Minimum Voting Power threshold is a Bronze DEX. The Foundation does not maintain Bronze connectors nor will we allocate bounties for them, but they may be maintained by a member of the community.

DEXs that don't meet the Minimum Voting Power threshold (100K) will be removed from the codebase.