## What changes were proposed in this pull request?
Adds SparkR API for FPGrowth: [SPARK-19825](https://issues.apache.org/jira/browse/SPARK-19825):
- `spark.fpGrowth` -model training.
- `freqItemsets` and `associationRules` methods with new corresponding generics.
- Scala helper: `org.apache.spark.ml.r. FPGrowthWrapper`
- unit tests.
## How was this patch tested?
Feature specific unit tests.
Author: zero323 <zero323@users.noreply.github.com>
Closes#17170 from zero323/SPARK-19825.
