## What changes were proposed in this pull request?

This PR continues the work from #11871 with the following changes:
* load English stopwords as default
* covert stopwords to list in Python
* update some tests and doc

## How was this patch tested?

Unit tests.

Closes #11871

cc: burakkose srowen

Author: Burak Köse <burakks41@gmail.com>
Author: Xiangrui Meng <meng@databricks.com>
Author: Burak KOSE <burakks41@gmail.com>

Closes #12843 from mengxr/SPARK-14050.