[SPARK-18857][SQL] Don't use `Iterator.duplicate` for `incrementalCollect` in Thrift Server

## What changes were proposed in this pull request?

To support `FETCH_FIRST`, SPARK-16563 used Scala `Iterator.duplicate`. However,
Scala `Iterator.duplicate` uses a **queue to buffer all items between both iterators**,
this causes GC and hangs for queries with large number of rows. We should not use this,
especially for `spark.sql.thriftServer.incrementalCollect`.

https://github.com/scala/scala/blob/2.12.x/src/library/scala/collection/Iterator.scala#L1262-L1300

## How was this patch tested?

Pass the existing tests.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #16440 from dongjoon-hyun/SPARK-18857.