Ensure notifications and browser_info are loaded in the extension

[philippjfr]

Load notifications and browser_info even when HoloViews is in sys.modules. Previously Holoviews being available would always force nb_loaded to True meaning that browser_info and notifications would never get displayed.

[codecov]

Codecov Report

Merging #5657 (8ba8dea) into main (af003b8) will increase coverage by 10.40%.
The diff coverage is 68.42%.

@@             Coverage Diff             @@
##             main    #5657       +/-   ##
===========================================
+ Coverage   73.70%   84.11%   +10.40%     
===========================================
  Files         288      288               
  Lines       41878    41879        +1     
===========================================
+ Hits        30866    35226     +4360     
+ Misses      11012     6653     -4359     

Flag	Coverage Δ
ui-tests	40.82% <68.42%> (?)
unitexamples-tests	73.71% <10.52%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
panel/io/convert.py	72.49% <ø> (+46.19%)	⬆️
panel/io/state.py	72.53% <ø> (+2.01%)	⬆️
panel/tests/ui/widgets/test_button.py	97.05% <100.00%> (+58.82%)	⬆️
panel/tests/ui/widgets/test_indicators.py	100.00% <100.00%> (+66.66%)	⬆️
panel/widgets/base.py	92.10% <50.00%> (ø)
panel/config.py	70.65% <16.66%> (+2.98%)	⬆️

... and 74 files with indirect coverage changes

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