[SPARK-19993][SQL] Caching logical plans containing subquery expressions does not work.

## What changes were proposed in this pull request?
The sameResult() method does not work when the logical plan contains subquery expressions.

**Before the fix**
```SQL
scala> val ds = spark.sql("select * from s1 where s1.c1 in (select s2.c1 from s2 where s1.c1 = s2.c1)")
ds: org.apache.spark.sql.DataFrame = [c1: int]

scala> ds.cache
res13: ds.type = [c1: int]

scala> spark.sql("select * from s1 where s1.c1 in (select s2.c1 from s2 where s1.c1 = s2.c1)").explain(true)
== Analyzed Logical Plan ==
c1: int
Project [c1#86]
+- Filter c1#86 IN (list#78 [c1#86])
   :  +- Project [c1#87]
   :     +- Filter (outer(c1#86) = c1#87)
   :        +- SubqueryAlias s2
   :           +- Relation[c1#87] parquet
   +- SubqueryAlias s1
      +- Relation[c1#86] parquet

== Optimized Logical Plan ==
Join LeftSemi, ((c1#86 = c1#87) && (c1#86 = c1#87))
:- Relation[c1#86] parquet
+- Relation[c1#87] parquet
```
**Plan after fix**
```SQL
== Analyzed Logical Plan ==
c1: int
Project [c1#22]
+- Filter c1#22 IN (list#14 [c1#22])
   :  +- Project [c1#23]
   :     +- Filter (outer(c1#22) = c1#23)
   :        +- SubqueryAlias s2
   :           +- Relation[c1#23] parquet
   +- SubqueryAlias s1
      +- Relation[c1#22] parquet

== Optimized Logical Plan ==
InMemoryRelation [c1#22], true, 10000, StorageLevel(disk, memory, deserialized, 1 replicas)
   +- *BroadcastHashJoin [c1#1, c1#1], [c1#2, c1#2], LeftSemi, BuildRight
      :- *FileScan parquet default.s1[c1#1] Batched: true, Format: Parquet, Location: InMemoryFileIndex[file:/Users/dbiswal/mygit/apache/spark/bin/spark-warehouse/s1], PartitionFilters: [], PushedFilters: [], ReadSchema: struct<c1:int>
      +- BroadcastExchange HashedRelationBroadcastMode(List((shiftleft(cast(input[0, int, true] as bigint), 32) | (cast(input[0, int, true] as bigint) & 4294967295))))
         +- *FileScan parquet default.s2[c1#2] Batched: true, Format: Parquet, Location: InMemoryFileIndex[file:/Users/dbiswal/mygit/apache/spark/bin/spark-warehouse/s2], PartitionFilters: [], PushedFilters: [], ReadSchema: struct<c1:int>
```
## How was this patch tested?
New tests are added to CachedTableSuite.

Author: Dilip Biswal <dbiswal@us.ibm.com>

Closes #17330 from dilipbiswal/subquery_cache_final.