Redesign Tabulator styles handling

[philippjfr]

Previously we were resetting the styles property on the model and keeping a local copy on the view. The problem with this is that the same model can be rendered again at a later stage and if when it was deleted the styles had been reset then it would render without the styles the second time. Therefore we take the simpler approach of including a random id in the styles so that even when the style hasn't changed it will still trigger updates.

[codecov]

Codecov Report

Merging #3175 (8222ae2) into master (3768a17) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3175   +/-   ##
=======================================
  Coverage   82.94%   82.94%           
=======================================
  Files         192      192           
  Lines       25520    25521    +1     
=======================================
+ Hits        21168    21169    +1     
  Misses       4352     4352           

Impacted Files	Coverage Δ
panel/models/tabulator.py	95.45% <100.00%> (ø)
panel/tests/widgets/test_tables.py	99.49% <100.00%> (ø)
panel/widgets/tables.py	84.78% <100.00%> (+0.01%)	⬆️

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