[SPARK-35791][SQL] Release on-going map properly for NULL-aware ANTI …

…join

### What changes were proposed in this pull request?

NULL-aware ANTI join (https://issues.apache.org/jira/browse/SPARK-32290) detects NULL join keys during building the map for `HashedRelation`, and will immediately return `HashedRelationWithAllNullKeys` without taking care of the map built already. Before returning `HashedRelationWithAllNullKeys`, the map needs to be freed properly to save memory and keep memory accounting correctly.

### Why are the changes needed?

Save memory and keep memory accounting correctly for the join query.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Existing unit tests introduced in #29104 .

Closes #32939 from c21/free-null-aware.

Authored-by: Cheng Su <chengsu@fb.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala

@@ -479,6 +479,7 @@ private[joins] object UnsafeHashedRelation {
           throw QueryExecutionErrors.cannotAcquireMemoryToBuildUnsafeHashedRelationError()
         }
       } else if (isNullAware) {
+        binaryMap.free()
         return HashedRelationWithAllNullKeys
       }
     }
@@ -1060,6 +1061,7 @@ private[joins] object LongHashedRelation {
         val key = rowKey.getLong(0)
         map.append(key, unsafeRow)
       } else if (isNullAware) {
+        map.free()
         return HashedRelationWithAllNullKeys
       }
     }