Fix draw_order not working

[Wumpf]

What

Draw order was not doing anything on 0.14!

The underlying issue was that the depth offset context system which converts draw order to depth offsets didn't iterate any entities since it used a iterator for entities.
This means we're now iterating a much larger entity set. I checked with the "many entities" manual test and the context system takes about 0.5ms for me in release there. This is kinda bad but it's not a big dent here (unfortunately) and it runs in parallel to the much slower transform context system.

This PR moves the (also broken due to heuristic changes) test from "api_test" to a release check with a description what should be observable.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: rerun.io/viewer
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!

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