Improve ipywidgets handling

[philippjfr]

The new comm library install a DummyComm unless we apply the patches in panel.io.ipywidget, so we handle this case and override the comm. Separately we must ensure that panel.io.ipywidget is loaded before ipywidgets_bokeh.

Fixes #2435

[codecov]

Codecov Report

Merging #4779 (2c02952) into main (a9a6da0) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #4779      +/-   ##
==========================================
- Coverage   73.17%   73.16%   -0.02%     
==========================================
  Files         268      268              
  Lines       37786    37786              
==========================================
- Hits        27651    27645       -6     
- Misses      10135    10141       +6     

Flag	Coverage Δ
unitexamples-tests	73.16% <0.00%> (-0.02%)	⬇️

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Impacted Files	Coverage Δ
panel/io/ipywidget.py	0.00% <0.00%> (ø)
panel/pane/ipywidget.py	53.22% <0.00%> (ø)

... and 4 files with indirect coverage changes

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