[SPARK-21306][ML] For branch 2.0, OneVsRest should support setWeightCol
The PR is related to #18554, and is modified for branch 2.0.
## What changes were proposed in this pull request?
add `setWeightCol` method for OneVsRest.
`weightCol` is ignored if classifier doesn't inherit HasWeightCol trait.
## How was this patch tested?
+ [x] add an unit test.
Author: Yan Facai (颜发才) <facai.yan@gmail.com>
Closes #18764 from facaiy/BUG/branch-2.0_OneVsRest_support_setWeightCol.
spark
9f670ce5 - [SPARK-21306][ML] For branch 2.0, OneVsRest should support setWeightCol
