Switch VTK colormap lookuptable serializer

[philippjfr]

Fixes #6627

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.85%. Comparing base (e9cc695) to head (e5a8d01).

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #6651       +/-   ##
===========================================
+ Coverage   39.99%   82.85%   +42.86%     
===========================================
  Files         313      313               
  Lines       46103    46119       +16     
===========================================
+ Hits        18438    38212    +19774     
+ Misses      27665     7907    -19758     

Flag	Coverage Δ
ui-tests	39.98% <0.00%> (-0.01%)	⬇️
unitexamples-tests	71.15% <100.00%> (?)

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