Use streaming search for faster time-to-first-result

[chrismwendt]

There's a nifty API called stream search https://sourcegraph.com/.api/search/stream?q=asdf which gives you first results quicker than via GraphQL. This could speed up some search-based code intel operations.

Open questions:

• How much of a latency improvement would we get? I'm seeing CodeIntelSearch requests taking ~110ms on Sourcegraph.com, which seems pretty fast already

Originally from Slack.