Arcade PR pipeline uploads GBs of pipeline artifacts unnecessarily

[premun]

The Arcade PR pipeline takes over 1 hour to finish while it's doing some unnecessary things:

• Uploading 6 GB of pipeline artifacts that are not used (it is upload in the Test phase at the very end)
• Uploading 4 GB in the build phase where I don't think the artifacts are used for anything (needs to be verified)

Furthermore, when building the test phase, we send unit tests to 4 queues to test the Helix SDK. However, we build the tests 4 times even though we probably can only do it once, however, this does only takes several minutes so not a high priority

[premun]

This has now been amplified by #8252 since we upload build artifacts from the test stages (needlessly as there is no more stage after that which would use them) and now we upload them from all the new stages:

Maybe we could do something about this?