Improve scene loading typings & fix loading race

[speigg]

More accurate typings for scene data / metadata.
More accurate typings for scene service state, and more understandable action names.
Ensure that scene data is available before systems can initialize.
Move loading progress logic into EngineService receptor.
Use useHookedEffect in LoadEngineWithScene and NetworkInstanceProvisioning.

Summary

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Checklist

• Pre-push checks pass npm run check
  • Linter passing via npm run lint
  • Unit & Integration tests passing via npm run test:packages
  • Docker build process passing via npm run build-client
• If this PR is still a WIP, convert to a draft
• When this PR is ready, mark it as "Ready for review"
• Changes have been manually QA'd
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QA Steps

1. git checkout pr_branch_name
2. npm install
3. npm run dev-reinit
4. npm run dev

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