eth_call over http slow on windows

[markspanbroek]

As observed in the integration tests of nim-codex, JSON-RPC calls to hardhat
using http (not websockets) are very slow. A single call to eth_call takes about 2-3 seconds.
This was also observed on fast machines. It seems to only occur on windows.

[markspanbroek]

I figured out what is causing this; apparently it takes windows 2-3 seconds to resolve "localhost" to "127.0.0.1" every time a JSON-RPC call is made over http 🤦. So you need to use "http://127.0.0.1:8545" instead of "http://localhost:8545" on windows. We should probably change the examples urls in nim-ethers to reflect this, and add a warning to the readme.