### What changes were proposed in this pull request?
1, `predictionCol` in `ml.classification` & `ml.clustering` add `NominalAttribute`
2, `rawPredictionCol` in `ml.classification` add `AttributeGroup` containing vectorsize=`numClasses`
3, `probabilityCol` in `ml.classification` & `ml.clustering` add `AttributeGroup` containing vectorsize=`numClasses`/`k`
4, `leafCol` in GBT/RF add `AttributeGroup` containing vectorsize=`numTrees`
5, `leafCol` in DecisionTree add `NominalAttribute`
6, `outputCol` in models in `ml.feature` add `AttributeGroup` containing vectorsize
7, `outputCol` in `UnaryTransformer`s in `ml.feature` add `AttributeGroup` containing vectorsize
### Why are the changes needed?
Appened metadata can be used in downstream ops, like `Classifier.getNumClasses`
There are many impls (like `Binarizer`/`Bucketizer`/`VectorAssembler`/`OneHotEncoder`/`FeatureHasher`/`HashingTF`/`VectorSlicer`/...) in `.ml` that append appropriate metadata in `transform`/`transformSchema` method.
However there are also many impls return no metadata in transformation, even some metadata like `vector.size`/`numAttrs`/`attrs` can be ealily inferred.
### Does this PR introduce any user-facing change?
Yes, add some metadatas in transformed dataset.
### How was this patch tested?
existing testsuites and added testsuites
Closes#26547 from zhengruifeng/add_output_vecSize.
Authored-by: zhengruifeng <ruifengz@foxmail.com>
Signed-off-by: zhengruifeng <ruifengz@foxmail.com>
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