Add pipeline stream name to containers as labels

[jlebon]

Feature Request

Desired Feature

The release controller wants to be able to tell from which stream an RHCOS build came from just by looking at its container image as found in the release payload. That way, it can link to the right stream in the RHCOS release browser.

Let's add a label for this to the image to make that easier. For consistency, we should probably add it to all the containers and not just the main one (i.e. the extensions container too).

Example Usage

UX to be discussed. We want to avoid passing switches; that won't work as nicely for the extensions container. Probably simplest is to drop a file in src/ at the top and have cosa pick up on that.

Other Information

See openshift/release-controller#503 (comment) and following.

[jlebon]

We should also fix #3480 when we do this.