insights: migrate compute search to the streaming endpoint

Created by: leonore

closes #33925 (closed)

This moves compute queries for both backend and just in time insights to the compute streaming endpoint.

Subsequent work will involve adding error returns to the API and handle them in our decoder.

Test plan

1. Compare insights created in stream vs non-stream, for both backend and just in time insights. The two queries I used were: patterntype:regexp file:go\.mod$ go\s*(\d\.\d+) and patterntype:regexp var\(--(.*color.*)\) lang:css (for JIT on github.com/sourcegraph/sourcegraph) Some comparison screenshots, from sourcegraph.test vs demo.sourcegraph.com. The slight differences in the backend insights are due to the differences in dates.