### What changes were proposed in this pull request?
This PR intends to fix the bug that does not apply right-padding for char types inside correlated subquries.
For example, a query below returns nothing in master, but a correct result is `c`.
```
scala> sql(s"CREATE TABLE t1(v VARCHAR(3), c CHAR(5)) USING parquet")
scala> sql(s"CREATE TABLE t2(v VARCHAR(5), c CHAR(7)) USING parquet")
scala> sql("INSERT INTO t1 VALUES ('c', 'b')")
scala> sql("INSERT INTO t2 VALUES ('a', 'b')")
scala> val df = sql("""
|SELECT v FROM t1
|WHERE 'a' IN (SELECT v FROM t2 WHERE t2.c = t1.c )""".stripMargin)
scala> df.show()
+---+
| v|
+---+
+---+
```
This is because `ApplyCharTypePadding` does not handle the case above to apply right-padding into `'abc'`. This PR modifies the code in `ApplyCharTypePadding` for handling it correctly.
```
// Before this PR:
scala> df.explain(true)
== Analyzed Logical Plan ==
v: string
Project [v#13]
+- Filter a IN (list#12 [c#14])
: +- Project [v#15]
: +- Filter (c#16 = outer(c#14))
: +- SubqueryAlias spark_catalog.default.t2
: +- Relation default.t2[v#15,c#16] parquet
+- SubqueryAlias spark_catalog.default.t1
+- Relation default.t1[v#13,c#14] parquet
scala> df.show()
+---+
| v|
+---+
+---+
// After this PR:
scala> df.explain(true)
== Analyzed Logical Plan ==
v: string
Project [v#43]
+- Filter a IN (list#42 [c#44])
: +- Project [v#45]
: +- Filter (c#46 = rpad(outer(c#44), 7, ))
: +- SubqueryAlias spark_catalog.default.t2
: +- Relation default.t2[v#45,c#46] parquet
+- SubqueryAlias spark_catalog.default.t1
+- Relation default.t1[v#43,c#44] parquet
scala> df.show()
+---+
| v|
+---+
| c|
+---+
```
This fix is lated to TPCDS q17; the query returns nothing because of this bug: https://github.com/apache/spark/pull/31886/files#r599333799
### Why are the changes needed?
Bugfix.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
Unit tests added.
Closes#31940 from maropu/FixCharPadding.
Authored-by: Takeshi Yamamuro <yamamuro@apache.org>
Signed-off-by: Takeshi Yamamuro <yamamuro@apache.org>
150769bced