`Downloader._write_directory()`: use `ByteStream.Read()`
Description
This corrects the Downloader._write_directory()
method so that files are queued to be batch-downloaded or downloaded individually using ByteStream.Read()
according to their sizes.
Changes proposed in this merge request:
-
Downloader._write_directory()
: change invocation offetch_file()
fordownload_file()
. The latter performs a size check before deciding which mechanism to use for the download.