Determine per-view overrides in parallel (-> faster many entities + many views on native)

[Wumpf]

Related

• part of Project: Performant visualization of scenes with large number of entities #8233

Description

Override determiniation (even if there are no overrides at all) can get very slow for many entities. This PR doesn't address that, but makes it parallel per-view. This alleviates the pain a little bit and was fairly straight forward to do.

Came up because I couldn't bear the sight in

• Add simple test script for testing out widely branched transform hierarchies #11437

Makes it neatly stacked if multithreading isn't opted out or you're running on the web

(this happens to be the slowest part in this synthetic scene which consists entirely of transforms, created via upcoming pixi run -e py python tests/python/many_entity_transforms/main.py --transforms-only)

[github-actions]

Web viewer built successfully.

Result	Commit	Link	Manifest
✅	6864a90	https://rerun.io/viewer/pr/11439	+nightly +main

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[abey79]

nice!