[SPARK-19896][SQL] Throw an exception if case classes have circular references in toDS

## What changes were proposed in this pull request?
If case classes have circular references below, it throws StackOverflowError;
```
scala> :pasge
case class classA(i: Int, cls: classB)
case class classB(cls: classA)

scala> Seq(classA(0, null)).toDS()
java.lang.StackOverflowError
  at scala.reflect.internal.Symbols$Symbol.info(Symbols.scala:1494)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$$anon$1.scala$reflect$runtime$SynchronizedSymbols$SynchronizedSymbol$$super$info(JavaMirrors.scala:66)
  at scala.reflect.runtime.SynchronizedSymbols$SynchronizedSymbol$$anonfun$info$1.apply(SynchronizedSymbols.scala:127)
  at scala.reflect.runtime.SynchronizedSymbols$SynchronizedSymbol$$anonfun$info$1.apply(SynchronizedSymbols.scala:127)
  at scala.reflect.runtime.Gil$class.gilSynchronized(Gil.scala:19)
  at scala.reflect.runtime.JavaUniverse.gilSynchronized(JavaUniverse.scala:16)
  at scala.reflect.runtime.SynchronizedSymbols$SynchronizedSymbol$class.gilSynchronizedIfNotThreadsafe(SynchronizedSymbols.scala:123)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$$anon$1.gilSynchronizedIfNotThreadsafe(JavaMirrors.scala:66)
  at scala.reflect.runtime.SynchronizedSymbols$SynchronizedSymbol$class.info(SynchronizedSymbols.scala:127)
  at scala.reflect.runtime.JavaMirrors$JavaMirror$$anon$1.info(JavaMirrors.scala:66)
  at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:48)
  at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:45)
  at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:45)
  at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:45)
  at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:45)
```
This pr added code to throw UnsupportedOperationException in that case as follows;
```
scala> :paste
case class A(cls: B)
case class B(cls: A)

scala> Seq(A(null)).toDS()
java.lang.UnsupportedOperationException: cannot have circular references in class, but got the circular reference of class B
  at org.apache.spark.sql.catalyst.ScalaReflection$.org$apache$spark$sql$catalyst$ScalaReflection$$serializerFor(ScalaReflection.scala:627)
  at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$9.apply(ScalaReflection.scala:644)
  at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$9.apply(ScalaReflection.scala:632)
  at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
  at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
  at scala.collection.immutable.List.foreach(List.scala:381)
  at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:241)
```

## How was this patch tested?
Added tests in `DatasetSuite`.

Author: Takeshi Yamamuro <yamamuro@apache.org>

Closes #17318 from maropu/SPARK-19896.