Respect TTL of a DNS record for proxy config.

[minwoox]

The methods in ProxyConfig take an InetSocketAddress as an argument. e.g. ProxyConfig.connect(InetSocketAddress) InetSocketAddress resolves the address only once when it's created so it doesn't respect TTL of a DNS record, thus the client will keep sending the request to the old proxy. We can probably take an Endpoint instead of InetSocketAddress and reimplement it to respect the TTL in the client.