make AutoMLExperiment public && some small refactor

[LittleLittleCloud]

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• There's a descriptive title that will make sense to other developers some time from now.
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[codecov]

Codecov Report

Merging #6173 (d4c38cd) into main (0e7e807) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #6173   +/-   ##
=======================================
  Coverage   68.29%   68.29%           
=======================================
  Files        1098     1098           
  Lines      242080   242080           
  Branches    25166    25166           
=======================================
+ Hits       165334   165338    +4     
+ Misses      70178    70174    -4     
  Partials     6568     6568           

Flag	Coverage Δ
Debug	68.29% <ø> (+<0.01%)	⬆️
production	62.75% <ø> (+<0.01%)	⬆️
test	88.82% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...ML.Transforms/Text/StopWordsRemovingTransformer.cs	86.23% <0.00%> (-0.15%)	⬇️
...soft.ML.Transforms/Text/WordEmbeddingsExtractor.cs	86.87% <0.00%> (+1.13%)	⬆️

[LittleLittleCloud]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[michaelgsharp]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).