Update page Parameter when pagination is 'local'

[maximlt]

Fixes #3647

By setting up the pageLoaded callback that is triggered on page change by Tabulator JS, and within which the page model attribute is set when pagination is 'local'. By the way this check is there to be explicit as I didn't see the callback being triggered when pagination is 'remote'.

[codecov]

Codecov Report

Merging #3704 (c1404fe) into master (b827be2) will increase coverage by 0.22%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3704      +/-   ##
==========================================
+ Coverage   83.32%   83.55%   +0.22%     
==========================================
  Files         207      207              
  Lines       29654    29654              
==========================================
+ Hits        24709    24777      +68     
+ Misses       4945     4877      -68     

Flag	Coverage Δ
ui-tests	31.90% <100.00%> (-0.01%)	⬇️
unitexamples-tests	78.19% <100.00%> (+0.27%)	⬆️

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Impacted Files	Coverage Δ
panel/tests/ui/widgets/test_tabulator.py	98.08% <100.00%> (ø)
panel/tests/util.py	84.37% <0.00%> (-1.05%)	⬇️
panel/util.py	86.36% <0.00%> (-0.38%)	⬇️
panel/io/server.py	76.56% <0.00%> (+0.20%)	⬆️
panel/io/reload.py	71.73% <0.00%> (+2.17%)	⬆️
panel/widgets/terminal.py	70.89% <0.00%> (+20.18%)	⬆️
panel/tests/widgets/test_terminal.py	58.87% <0.00%> (+22.42%)	⬆️

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