snowbridge: allow account conversion for Ethereum accounts (#6221)
Replace `GlobalConsensusEthereumConvertsFor` with `EthereumLocationsConverterFor` that allows `Location` to `AccountId` conversion for the Ethereum network root as before, but also for Ethereum contracts and accounts. The new converter only matches explicit `parents: 2` Ethereum locations, meaning it should be used only on/by parachains.