Correctly handle resource mode in conversion

[philippjfr]

Fixes issues with resolving Tabulator theme resources correctly in converted Panel application.

Also ensures that panel convert tests are run against a locally built wheel.

[codecov]

Codecov Report

Merging #3967 (063008d) into master (86cb7ea) will decrease coverage by 0.01%.
The diff coverage is 91.93%.

@@            Coverage Diff             @@
##           master    #3967      +/-   ##
==========================================
- Coverage   83.72%   83.71%   -0.02%     
==========================================
  Files         223      223              
  Lines       32984    33008      +24     
==========================================
+ Hits        27615    27631      +16     
- Misses       5369     5377       +8     

Flag	Coverage Δ
ui-tests	37.29% <90.32%> (+0.35%)	⬆️
unitexamples-tests	74.89% <20.96%> (-0.07%)	⬇️

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Impacted Files	Coverage Δ
panel/io/convert.py	67.96% <87.50%> (-0.90%)	⬇️
panel/tests/ui/io/test_convert.py	95.28% <91.83%> (-3.57%)	⬇️
panel/io/resources.py	86.80% <100.00%> (+0.09%)	⬆️
panel/models/tabulator.py	97.77% <100.00%> (ø)
panel/widgets/tables.py	88.31% <100.00%> (ø)
panel/io/state.py	69.89% <0.00%> (-0.37%)	⬇️
panel/tests/util.py	89.32% <0.00%> (+0.97%)	⬆️

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