[SPARK-11485][SQL] Make DataFrameHolder and DatasetHolder public.

[rxin]

These two classes should be public, since they are used in public code.

[SparkQA]

Test build #44957 has finished for PR 9445 at commit ff07bad.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #44960 has finished for PR 9445 at commit f623c5d.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):\n * case class ExecutorLostFailure(\n

[SparkQA]

Test build #44979 has finished for PR 9445 at commit f75c4a5.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

cc @marmbrus

[cloud-fan]

This is not right, we also support Seq of Int. Maybe just say "a local Seq"

[rxin]

fixed

[SparkQA]

Test build #45009 has finished for PR 9445 at commit a14ed6c.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):\n * case class ExecutorLostFailure(\n * public class JavaIsotonicRegressionExample\n * public class JavaNaiveBayesExample\n * case class DecimalLit(chars: String) extends Token\n * case class UnresolvedStar(target: Option[Seq[String]]) extends Star with Unevaluable\n * case class Exchange(\n * class CoalescedPartitioner(val parent: Partitioner, val partitionStartIndices: Array[Int])\n

[yhuai]

test this please

[yhuai]

LGTM

[rxin]

Merging this.

[SparkQA]

Test build #1979 has finished for PR 9445 at commit a14ed6c.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.