WIP: anywidget-based rendercanvas

[gselzer]

This PR switches to the anywidget-backed jupyter-rfb, which we avoided for reasons described in #63.

It should be a WIP until jupyter-rfb gets a new >1.0.2 release

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 84.30%. Comparing base (d0d3ede) to head (08a270e).

Files with missing lines	Patch %	Lines
src/scenex/app/_jupyter.py	0.00%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (85.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #84      +/-   ##
==========================================
- Coverage   87.64%   84.30%   -3.35%     
==========================================
  Files          64       64              
  Lines        3287     3287              
==========================================
- Hits         2881     2771     -110     
- Misses        406      516     +110     

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