What

• Closes Split ViewportBlueprint in its own crate #5421
• Unlocks Split context menu in their own crate #6414
• Unlocks Split blueprint tree panel UI in its own crate #6415

This enable more general access to manipulating the blueprint and unlock further crate splitting.

TODO

• delete the traits in data_query.rs and use concrete types instead
• move the UI function introduced by Andreas back to re_space_view

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 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!

• PR Build Summary
• Recent benchmark results
• Wasm size tracking

To run all checks from main, comment on the PR with @rerun-bot full-check.