Functional Scene Loader Refactor

[HexaField]

Summary

Changes the scene loader to be entirely functional. Replace some callbacks with EngineEvents and simplifies the scene network object handling

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
• Changes reviewed by at least 2 approved reviewers

References

#4311

QA Steps

1. git checkout refactor-scene-loader
2. npm install
3. npm run dev-reinit
4. npm run dev

List any additional steps required to QA the changes of this PR, as well as any supplemental images or videos.

Reviewers

@HexaField @speigg @NateTheGreatt