[server] Use image-builder from workspace cluster (feature flag: "movedImageBuilder")

[geropl]

Description

This is part II of a translation from Chris' PR. To be able to move forward with this, it got split into two:

1. The deprecation of the old log retrieval mechanism in this PR (feature flag: "deprecateOldImageLogsMechanism")
2. Make server talk to ws-manager for image builds (this PR) (feature flag: "movedImageBuilder")

The idea is to get both merged, and be able to test and iterate independently.

/cc @kylos101

Note 1: All formatting should be in commit 1, so it's sufficient to review commit 2 alone.

Note 2: Commit 3 + 4 do not strictly belong into this PR but I left them here because they ease testing. 🧘

Related Issue(s)

Fixes #9248

Context: #9337

How to test

• preview env: create a team with a name containing imgbldr and project (e.g. on this test repo) (the imgbldr triggers feature flags movedImageBuilder and deprecateOldImageLogsMechanism, cmp. here)
• push a commit, for instance to this branch
• open a workspace on that branch
• observe that workspace start and the streaming of image build logs works as expected
• check server logs for the line image-builder in workspace cluster to validate you actually used the new mechanism

Release Notes

NONE

Documentation

Werft options:

• /werft with-preview

[geropl]

/werft run

👍 started the job as gitpod-build-gpl-imgbldr.5
(with .werft/ from main)

[sagor999]

did not test, only reviewed one file for which I am code owner and that one LGTM. 🙏