[SPARK-3135] Avoid extra mem copy in TorrentBroadcast via ByteArrayChunkOutputStream

This also enables supporting broadcast variables larger than 2G.

Author: Reynold Xin <rxin@apache.org>

Closes #2054 from rxin/ByteArrayChunkOutputStream and squashes the following commits:

618d9c8 [Reynold Xin] Code review.
93f5a51 [Reynold Xin] Added comments.
ee88e73 [Reynold Xin] to -> until
bbd1cb1 [Reynold Xin] Renamed a variable.
36f4d01 [Reynold Xin] Sort imports.
8f1a8eb [Reynold Xin] [SPARK-3135] Created ByteArrayChunkOutputStream and used it to avoid memory copy in TorrentBroadcast.