[SPARK-16888][SQL] Implements eval method for expression AssertNotNull

## What changes were proposed in this pull request?

Implements `eval()` method for expression `AssertNotNull` so that we can convert local projection on LocalRelation to another LocalRelation.

### Before change:
```
scala> import org.apache.spark.sql.catalyst.dsl.expressions._
scala> import org.apache.spark.sql.catalyst.expressions.objects.AssertNotNull
scala> import org.apache.spark.sql.Column
scala> case class A(a: Int)
scala> Seq((A(1),2)).toDS().select(new Column(AssertNotNull("_1".attr, Nil))).explain

java.lang.UnsupportedOperationException: Only code-generated evaluation is supported.
  at org.apache.spark.sql.catalyst.expressions.objects.AssertNotNull.eval(objects.scala:850)
  ...
```

### After the change:
```
scala> Seq((A(1),2)).toDS().select(new Column(AssertNotNull("_1".attr, Nil))).explain(true)

== Parsed Logical Plan ==
'Project [assertnotnull('_1) AS assertnotnull(_1)#5]
+- LocalRelation [_1#2, _2#3]

== Analyzed Logical Plan ==
assertnotnull(_1): struct<a:int>
Project [assertnotnull(_1#2) AS assertnotnull(_1)#5]
+- LocalRelation [_1#2, _2#3]

== Optimized Logical Plan ==
LocalRelation [assertnotnull(_1)#5]

== Physical Plan ==
LocalTableScan [assertnotnull(_1)#5]
```

## How was this patch tested?

Unit test.

Author: Sean Zhong <seanzhong@databricks.com>

Closes #14486 from clockfly/assertnotnull_eval.

0 files changed, 0 insertions, 0 deletions