Add real owner to imagebuild metadata

[Furisto]

Description

Add real owner to imagebuild metadata

Related Issue(s)

n.a.

How to test

• Start image build in preview environment e.g. https://fo-imgbuild-owner.staging.gitpod-dev.com/#imagebuild/https://github.com/gitpod-io/gitpod
• Verify that owner label on the pod is the id of the user that triggered the imagebuild and not image-builder

Labels:       app=gitpod
              component=workspace
              gitpod.io/networkpolicy=default
              gpwsman=true
              headless=true
              metaID=db0de155-4a44-4d24-874a-f28d219dfeb1
              owner=b8a478cf-8488-44e1-a735-c155086c5095
              workspaceID=db0de155-4a44-4d24-874a-f28d219dfeb1
              workspaceType=imagebuild

• Use gcptl imagebuilds list -> imagebuild should still be listable

Notes for reviews

The push of the imagebuild to the registry fails in the preview environment, but this also happens without my changes.

Release Notes

None

[geropl]

Note that it's not defined what the "real owner" of an image build is, exactly. Calling it "triggered by" though makes sense.

[geropl]

Code LGTM, sans the off-topic disucssion about "workspace ownership".

[Furisto]

Hey @csweichel can you approve this PR if you do not have any further concerns?

[geropl]

@csweichel friendly pin so we can get this one in. 🙃

[csweichel]

sorry for the delay