## What changes were proposed in this pull request?
register following classes in Kryo:
"org.apache.spark.ml.stat.distribution.MultivariateGaussian",
"org.apache.spark.mllib.stat.distribution.MultivariateGaussian"
## How was this patch tested?
added tests
Due to existing module dependency, I can not import spark-core in mllib-local's testsuits, so I do not add testsuite in `org.apache.spark.ml.stat.distribution.MultivariateGaussianSuite`.
And I notice that class `ClusterStats` in `ClusteringEvaluator` is registered in a different way, should it be modified to keep in line with others in ML? srowen
Closes#22974 from zhengruifeng/kryo_MultivariateGaussian.
Authored-by: zhengruifeng <ruifengz@foxmail.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>
91405b3b6e