[SPARK-28599][SQL] Fix Execution Time and Duration column sorting for ThriftServerSessionPage

This PR add support sorting `Execution Time` and `Duration` columns for `ThriftServerSessionPage`.

Previously, it's not sorted correctly.

Yes.

Manually do the following and test sorting on those columns in the Spark Thrift Server Session Page.
```
$ sbin/start-thriftserver.sh
$ bin/beeline -u jdbc:hive2://localhost:10000
0: jdbc:hive2://localhost:10000> create table t(a int);
+---------+--+
| Result  |
+---------+--+
+---------+--+
No rows selected (0.521 seconds)
0: jdbc:hive2://localhost:10000> select * from t;
+----+--+
| a  |
+----+--+
+----+--+
No rows selected (0.772 seconds)
0: jdbc:hive2://localhost:10000> show databases;
+---------------+--+
| databaseName  |
+---------------+--+
| default       |
+---------------+--+
1 row selected (0.249 seconds)
```

**Sorted by `Execution Time` column**:
![image](https://user-images.githubusercontent.com/5399861/65387476-53038900-dd7a-11e9-885c-fca80287f550.png)

**Sorted by `Duration` column**:
![image](https://user-images.githubusercontent.com/5399861/65387481-6e6e9400-dd7a-11e9-9318-f917247efaa8.png)

Closes #25892 from wangyum/SPARK-28599.

Authored-by: Yuming Wang <yumwang@ebay.com>
Signed-off-by: Dongjoon Hyun <dhyun@apple.com>

Author: wangyum

sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/ui/ThriftServerSessionPage.scala

@@ -100,7 +100,8 @@ private[ui] class ThriftServerSessionPage(parent: ThriftServerTab)
           <td>{info.groupId}</td>
           <td>{formatDate(info.startTimestamp)}</td>
           <td>{formatDate(info.finishTimestamp)}</td>
-          <td>{formatDurationOption(Some(info.totalTime))}</td>
+          <td sorttable_customkey={info.totalTime.toString}>
+            {formatDurationOption(Some(info.totalTime))}</td>
           <td>{info.statement}</td>
           <td>{info.state}</td>
           {errorMessageCell(detail)}