## What changes were proposed in this pull request?

This PR proposes to support _not_ trimming the white spaces when writing out. These are `false` by default in CSV reading path but these are `true` by default in CSV writing in univocity parser.

Both `ignoreLeadingWhiteSpace` and `ignoreTrailingWhiteSpace` options are not being used for writing and therefore, we are always trimming the white spaces.

It seems we should provide a way to keep this white spaces easily.

WIth the data below:

```scala
val df = spark.read.csv(Seq("a , b  , c").toDS)
df.show()
```

```
+---+----+---+
|_c0| _c1|_c2|
+---+----+---+
| a | b  |  c|
+---+----+---+
```

**Before**

```scala
df.write.csv("/tmp/text.csv")
spark.read.text("/tmp/text.csv").show()
```

```
+-----+
|value|
+-----+
|a,b,c|
+-----+
```

It seems this can't be worked around via `quoteAll` too.

```scala
df.write.option("quoteAll", true).csv("/tmp/text.csv")
spark.read.text("/tmp/text.csv").show()
```
```
+-----------+
|      value|
+-----------+
|"a","b","c"|
+-----------+
```

**After**

```scala
df.write.option("ignoreLeadingWhiteSpace", false).option("ignoreTrailingWhiteSpace", false).csv("/tmp/text.csv")
spark.read.text("/tmp/text.csv").show()
```

```
+----------+
|     value|
+----------+
|a , b  , c|
+----------+
```

Note that this case is possible in R

```r
> system("cat text.csv")
f1,f2,f3
a , b  , c
> df <- read.csv(file="text.csv")
> df
  f1   f2 f3
1 a   b    c
> write.csv(df, file="text1.csv", quote=F, row.names=F)
> system("cat text1.csv")
f1,f2,f3
a , b  , c
```

## How was this patch tested?

Unit tests in `CSVSuite` and manual tests for Python.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #17310 from HyukjinKwon/SPARK-18579.