net/http: the client ignores Transport.Proxy and DialContext, so a proxied request goes direct #102

The netdev client in http/client.go dials with net.Dial or tls.Dial on the request host. It does not use Transport.Dial, DialContext, Proxy or TLSClientConfig. The field comments say so, but a program that sets a SOCKS5 or HTTP proxy for privacy gets a direct connection with no error.

I hit this with a skywire visor in the browser under TinyGo. Its web browsing is set up to go through a SOCKS5 proxy, and it went out directly from my own IP instead.

The fix in my fork dials through DialContext or Dial, speaks SOCKS5 (RFC 1928 and 1929) and HTTP CONNECT for Proxy, and does TLS with a clone of TLSClientConfig. It also applies the context deadline to the connection. I tested it under TinyGo on js/wasm and native linux, and also with Go. 5b8868f builds on #83. I can open a PR once I am able to again.