Please make TLS support optional

[joshtriplett]

Sometimes, I only need http support, not https; for instance, the instance metadata services in cloud environments only need http. For such cases, I would like to be able to use surf with the async-h1 backend and no TLS stack.

[brightly-salty]

I'd like to take a swing at this and submit a PR if it would be accepted.

[Fishrock123]

Needs support in http-client. We should support this.

[Fishrock123]

@brightly-salty are you still interested in this?

I think that the h1_client in http-client already supports running without tls, but surf's feature flags do not.

[brightly-salty]

Sure @Fishrock123 , sorry about that, must've slipped my mind. I'd be happy to work on it, I think it's just making a feature flag and configuring the tls-using code based on that?

[Fishrock123]

I think it would mostly need to be an alternate feature flag on Surf, probably something like h1-client-no-tls.