[SPARK-27986][SQL][FOLLOWUP] Respect filter in sql/toString of AggregateExpression
### What changes were proposed in this pull request?
This pr intends to add filter information in the explain output of an aggregate (This is a follow-up of #26656).
Without this pr:
```
scala> sql("select k, SUM(v) filter (where v > 3) from t group by k").explain(true)
== Parsed Logical Plan ==
'Aggregate ['k], ['k, unresolvedalias('SUM('v, ('v > 3)), None)]
+- 'UnresolvedRelation [t]
== Analyzed Logical Plan ==
k: int, sum(v): bigint
Aggregate [k#0], [k#0, sum(cast(v#1 as bigint)) AS sum(v)#3L]
+- SubqueryAlias `default`.`t`
+- Relation[k#0,v#1] parquet
== Optimized Logical Plan ==
Aggregate [k#0], [k#0, sum(cast(v#1 as bigint)) AS sum(v)#3L]
+- Relation[k#0,v#1] parquet
== Physical Plan ==
HashAggregate(keys=[k#0], functions=[sum(cast(v#1 as bigint))], output=[k#0, sum(v)#3L])
+- Exchange hashpartitioning(k#0, 200), true, [id=#20]
+- HashAggregate(keys=[k#0], functions=[partial_sum(cast(v#1 as bigint))], output=[k#0, sum#7L])
+- *(1) ColumnarToRow
+- FileScan parquet default.t[k#0,v#1] Batched: true, DataFilters: [], Format: Parquet, Location: InMemoryFileIndex[file:/Users/maropu/Repositories/spark/spark-master/spark-warehouse/t], PartitionFilters: [], PushedFilters: [], ReadSchema: struct<k:int,v:int>
scala> sql("select k, SUM(v) filter (where v > 3) from t group by k").show()
+---+------+
| k|sum(v)|
+---+------+
+---+------+
```
With this pr:
```
scala> sql("select k, SUM(v) filter (where v > 3) from t group by k").explain(true)
== Parsed Logical Plan ==
'Aggregate ['k], ['k, unresolvedalias('SUM('v, ('v > 3)), None)]
+- 'UnresolvedRelation [t]
== Analyzed Logical Plan ==
k: int, sum(v) FILTER (v > 3): bigint
Aggregate [k#0], [k#0, sum(cast(v#1 as bigint)) filter (v#1 > 3) AS sum(v) FILTER (v > 3)#5L]
+- SubqueryAlias `default`.`t`
+- Relation[k#0,v#1] parquet
== Optimized Logical Plan ==
Aggregate [k#0], [k#0, sum(cast(v#1 as bigint)) filter (v#1 > 3) AS sum(v) FILTER (v > 3)#5L]
+- Relation[k#0,v#1] parquet
== Physical Plan ==
HashAggregate(keys=[k#0], functions=[sum(cast(v#1 as bigint))], output=[k#0, sum(v) FILTER (v > 3)#5L])
+- Exchange hashpartitioning(k#0, 200), true, [id=#20]
+- HashAggregate(keys=[k#0], functions=[partial_sum(cast(v#1 as bigint)) filter (v#1 > 3)], output=[k#0, sum#9L])
+- *(1) ColumnarToRow
+- FileScan parquet default.t[k#0,v#1] Batched: true, DataFilters: [], Format: Parquet, Location: InMemoryFileIndex[file:/Users/maropu/Repositories/spark/spark-master/spark-warehouse/t], PartitionFilters: [], PushedFilters: [], ReadSchema: struct<k:int,v:int>
scala> sql("select k, SUM(v) filter (where v > 3) from t group by k").show()
+---+---------------------+
| k|sum(v) FILTER (v > 3)|
+---+---------------------+
+---+---------------------+
```
### Why are the changes needed?
For better usability.
### Does this PR introduce any user-facing change?
No.
### How was this patch tested?
Manually.
Closes #27198 from maropu/SPARK-27986-FOLLOWUP.
Authored-by: Takeshi Yamamuro <yamamuro@apache.org>
Signed-off-by: Takeshi Yamamuro <yamamuro@apache.org>
a3a42b30d0