[SPARK-35378][SQL][FOLLOWUP] isLocal should consider CommandResult

### What changes were proposed in this pull request?
apache#32513 added the case class `CommandResult` so as we can eagerly execute command locally. But we forgot to update
`isLocal` of `Dataset`.

### Why are the changes needed?
`Dataset.isLocal` should consider `CommandResult`.

### Does this PR introduce _any_ user-facing change?
Yes. If the SQL plan is `CommandResult`, `Dataset.isLocal` must return true.

### How was this patch tested?
No test.

Closes apache#32963 from beliefer/SPARK-35378-followup2.

Authored-by: gengjiaan <gengjiaan@360.cn>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

Author: beliefer

sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala

@@ -597,7 +597,8 @@ class Dataset[T] private[sql](
    * @group basic
    * @since 1.6.0
    */
-  def isLocal: Boolean = logicalPlan.isInstanceOf[LocalRelation]
+  def isLocal: Boolean = logicalPlan.isInstanceOf[LocalRelation] ||
+    logicalPlan.isInstanceOf[CommandResult]
 
   /**
    * Returns true if the `Dataset` is empty.

sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala

@@ -2907,6 +2907,13 @@ class DataFrameSuite extends QueryTest
       }
     }
   }
+
+  test("isLocal should consider CommandResult and LocalRelation") {
+    val df1 = sql("SHOW TABLES")
+    assert(df1.isLocal)
+    val df2 = (1 to 10).toDF()
+    assert(df2.isLocal)
+  }
 }
 
 case class GroupByKey(a: Int, b: Int)