Improve request handling for remote pagination on Tabulator

[philippjfr]

Patches ajax requests handling during initialization of the Tabulator so no request is ever sent and ensures Tabulator initialized with None works when paginated.

[codecov]

Codecov Report

Merging #2265 (202daa5) into master (50386e0) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2265      +/-   ##
==========================================
- Coverage   83.64%   83.61%   -0.03%     
==========================================
  Files         183      183              
  Lines       21899    21928      +29     
==========================================
+ Hits        18318    18336      +18     
- Misses       3581     3592      +11     

Impacted Files	Coverage Δ
panel/widgets/tables.py	84.07% <100.00%> (ø)
panel/pane/vtk/synchronizable_serializer.py	77.32% <0.00%> (-0.87%)	⬇️
panel/param.py	87.81% <0.00%> (-0.30%)	⬇️
panel/pane/vtk/vtk.py	96.38% <0.00%> (-0.01%)	⬇️
panel/pane/vtk/enums.py	100.00% <0.00%> (ø)
panel/models/vtk.py	98.48% <0.00%> (+0.02%)	⬆️

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