## What changes were proposed in this pull request?
Handle the case when ParsedStatement subclass has a Map field but not of type Map[String, String].
In ParsedStatement.productIterator, `case mapArg: Map[_, _]` can match any Map type due to type erasure, thus causing `asInstanceOf[Map[String, String]]` to throw ClassCastException.
The following test reproduces the issue:
```
case class TestStatement(p: Map[String, Int]) extends ParsedStatement {
override def output: Seq[Attribute] = Nil
override def children: Seq[LogicalPlan] = Nil
}
TestStatement(Map("abc" -> 1)).toString
```
Changing the code to `case mapArg: Map[String, String]` will not help due to type erasure. As a matter of fact, compiler gives this warning:
```
Warning:(41, 18) non-variable type argument String in type pattern
scala.collection.immutable.Map[String,String] (the underlying of Map[String,String])
is unchecked since it is eliminated by erasure
case mapArg: Map[String, String] =>
```
## How was this patch tested?
Add 2 unit tests.
Closes#24800 from jzhuge/SPARK-27947.
Authored-by: John Zhuge <jzhuge@apache.org>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
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