[SPARK-17583][SQL] Remove uesless rowSeparator variable and set auto-expanding...

[SPARK-17583][SQL] Remove uesless rowSeparator variable and set auto-expanding buffer as default for maxCharsPerColumn option in CSV

## What changes were proposed in this pull request?

This PR includes the changes below:

1. Upgrade Univocity library from 2.1.1 to 2.2.1

  This includes some performance improvement and also enabling auto-extending buffer in `maxCharsPerColumn` option in CSV. Please refer the [release notes](https://github.com/uniVocity/univocity-parsers/releases).

2. Remove useless `rowSeparator` variable existing in `CSVOptions`

  We have this unused variable in [CSVOptions.scala#L127](https://github.com/apache/spark/blob/29952ed096fd2a0a19079933ff691671d6f00835/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/csv/CSVOptions.scala#L127) but it seems possibly causing confusion that it actually does not care of `\r\n`. For example, we have an issue open about this, [SPARK-17227](https://issues.apache.org/jira/browse/SPARK-17227), describing this variable.

  This variable is virtually not being used because we rely on `LineRecordReader` in Hadoop which deals with only both `\n` and `\r\n`.

3. Set the default value of `maxCharsPerColumn` to auto-expending.

  We are setting 1000000 for the length of each column. It'd be more sensible we allow auto-expending rather than fixed length by default.

  To make sure, using `-1` is being described in the release note, [2.2.0](https://github.com/uniVocity/univocity-parsers/releases/tag/v2.2.0).

## How was this patch tested?

N/A

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #15138 from HyukjinKwon/SPARK-17583.