compute: add stream client for match context compute type

Created by: coury-clark

Adds a client similar to the main search stream client for the compute stream endpoint, but scoped to the MatchContext type. Longer term there is probably a better design for this considering the different "modes" of this API, but for now this solves our needs and doesn't seem too burdensome to change.

Test plan

This is really just a partial PR as part of a larger change, but I did include a test to decode a real stream result.