Draft: introduce concepts of App vs Recording Blueprint

[jleibs]

What

• Builds on top of: Enable selecting data sources and blueprints and recordings in them #5646

• Initial ground work supporting: Allow user to switch between "app blueprint" and "recording blueprint" #5640

Plenty left to do before this is ready:

• Make state visually clear
• Button to toggle
• Python API to choose whether this is a recording-blueprint or an app-blueprint

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: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• 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
• Docs preview
• Examples preview
• Recent benchmark results
• Wasm size tracking

[github-actions]

Size changes

Name	emilk/better-store-selection-view	5657/merge	Change
rrt-star.rrd	28.24 MiB	3.73 MiB	-86.79%