[SPARK-3142][MLLIB] output shuffle data directly in Word2Vec

Sorry I didn't realize this in #2043. Ishiihara

Author: Xiangrui Meng <meng@databricks.com>

Closes #2049 from mengxr/more-w2v and squashes the following commits:

050b1c5 [Xiangrui Meng] output shuffle data directly

(cherry picked from commit 0a984aa155fb7f532fe87620dcf1a2814c5b8b49)
Signed-off-by: Xiangrui Meng <meng@databricks.com>