refactor: improve code smell for postprocessing

[zhaoyongjie]

🏆 Enhancements
No functional changes, some refactor for postprocessing. Added boxplotOperator, contributionOperator and prophetOperator.

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[codecov]

Codecov Report

Merging #1368 (e688034) into master (e48afb9) will increase coverage by 0.17%.
The diff coverage is 95.83%.

@@            Coverage Diff             @@
##           master    #1368      +/-   ##
==========================================
+ Coverage   30.18%   30.35%   +0.17%     
==========================================
  Files         492      495       +3     
  Lines        9886     9896      +10     
  Branches     1666     1666              
==========================================
+ Hits         2984     3004      +20     
+ Misses       6655     6648       -7     
+ Partials      247      244       -3     

Impacted Files	Coverage Δ
...ins/plugin-chart-echarts/src/BoxPlot/buildQuery.ts	83.33% <0.00%> (+36.27%)	⬆️
plugins/plugin-chart-echarts/src/BoxPlot/types.ts	0.00% <ø> (ø)
.../plugin-chart-echarts/src/Timeseries/buildQuery.ts	50.00% <ø> (+25.00%)	⬆️
...ui-chart-controls/src/operators/boxplotOperator.ts	100.00% <100.00%> (ø)
...art-controls/src/operators/contributionOperator.ts	100.00% <100.00%> (ø)
...ui-chart-controls/src/operators/prophetOperator.ts	100.00% <100.00%> (ø)

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[michael-s-molina]

Can you avoid nesting tests? You can just use test on the top level.

[zhaoyongjie]

nice catch!

[michael-s-molina]

LGTM. Thanks for improving the code organization.