Add PCA and SVD to PySpark's wrappers for `RowMatrix` and `IndexedRowMatrix` (SVD only).

Based on #7963, updated.

## How was this patch tested?

New doc tests and unit tests. Ran all examples locally.

Author: MechCoder <manojkumarsivaraj334@gmail.com>
Author: Nick Pentreath <nickp@za.ibm.com>

Closes #17621 from MLnick/SPARK-6227-pyspark-svd-pca.