Followup fix and improvements on SchemaConformingTransformerV2

[lnbest0707-uber]

tags: feature bugfix
Followup from PR #12788 with:

• Getter/setter fix on SchemaConformingTransformerV2Config
• Schema and config validation improvement
• String type single value field ser/deser improvement
• Column - JsonKeyPath mapping improvement
• Unit test improvement with more comprehensive case coverage

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 40.00000% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 62.21%. Comparing base (59551e4) to head (1e097f1).
Report is 302 commits behind head on master.

Files	Patch %	Lines
...cordtransformer/SchemaConformingTransformerV2.java	50.00%	9 Missing and 3 partials ⚠️
...ingestion/SchemaConformingTransformerV2Config.java	0.00%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12932      +/-   ##
============================================
+ Coverage     61.75%   62.21%   +0.46%     
+ Complexity      207      198       -9     
============================================
  Files          2436     2503      +67     
  Lines        133233   136517    +3284     
  Branches      20636    21125     +489     
============================================
+ Hits          82274    84933    +2659     
- Misses        44911    45310     +399     
- Partials       6048     6274     +226     

Flag	Coverage Δ
custom-integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration	<0.01% <0.00%> (-0.01%)	⬇️
integration1	<0.01% <0.00%> (-0.01%)	⬇️
integration2	0.00% <0.00%> (ø)
java-11	62.17% <40.00%> (+0.46%)	⬆️
java-21	62.09% <40.00%> (+0.47%)	⬆️
skip-bytebuffers-false	62.19% <40.00%> (+0.44%)	⬆️
skip-bytebuffers-true	62.07% <40.00%> (+34.34%)	⬆️
temurin	62.21% <40.00%> (+0.46%)	⬆️
unittests	62.20% <40.00%> (+0.46%)	⬆️
unittests1	46.69% <0.00%> (-0.20%)	⬇️
unittests2	28.00% <40.00%> (+0.27%)	⬆️

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