[SPARK-3108][MLLIB] add predictOnValues to StreamingLR and fix predictOn

It is useful in streaming to allow users to carry extra data with the prediction, for monitoring the prediction error for example. freeman-lab

Author: Xiangrui Meng <meng@databricks.com>

Closes #2023 from mengxr/predict-on-values and squashes the following commits:

cac47b8 [Xiangrui Meng] add classtag
2821b3b [Xiangrui Meng] use mapValues
0925efa [Xiangrui Meng] add predictOnValues to StreamingLR and fix predictOn