PoolHedger can receive ETH directly from anyone
A `receive()` function has been added to GMXFuturesPoolHedger, so that it is able to receive ETH from GMX as request refunds. However, it is not advisable to have an open `receive()` function if it is not necessary. Users may wrongly send ETH directly to PoolHedger and lose it forever.\\n```\\n           receive() external payable {}\\n```\\n
Add a msg.sender check in the receive() function, and make sure sender is positionRouter.
```\\n           receive() external payable {}\\n```\\n