[SPARK-15618][SQL][MLLIB] Use SparkSession.builder.sparkContext if applicable.

## What changes were proposed in this pull request?

This PR changes function `SparkSession.builder.sparkContext(..)` from **private[sql]** into **private[spark]**, and uses it if applicable like the followings.
```
- val spark = SparkSession.builder().config(sc.getConf).getOrCreate()
+ val spark = SparkSession.builder().sparkContext(sc).getOrCreate()
```

## How was this patch tested?

Pass the existing Jenkins tests.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #13365 from dongjoon-hyun/SPARK-15618.