Support loading .rbl blueprint files

[emilk]

What

• Part of Support for working with blueprint files #5294

This implements loading of blueprint files (.rbl) on native and on web, using either drag-and-drop of the Open… command.

One shortcoming of the approach in this PR is documented here:

• Handle loading of blueprint with same StoreId as active blueprint #5514

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
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[jleibs]

I'm open to merging as is out of expediency, but as noted, this introduces an issue when using blueprints with connect, especially on recordings that stream for longer amounts of time.

[jleibs]

While this is definitely an improvement for the file-open use-case, moving this here regresses the current blueprint-on-connect behavior.

Because blueprint and recording share the same channel, the blueprint now won't be activated until the channel is closed.

You can see this issue by adding:

import time
time.sleep(5)

to the end of examples/python/blueprint/main.py

This causes the saved blueprint to load first. And then after the timeout when the whole connection is closed, the blueprint loads.

This alone is insufficient for #5297... we still need some kind of safe-to-load marker inside the stream.

[emilk]

ouch; good point…

[emilk]

Yeah, I might merge this and then start work on #5297

[github-actions]

Size changes

Name	main	5513/merge	Change
arkit_scenes.rrd	39.43 MiB	40.34 MiB	+2.31%