### What changes were proposed in this pull request?
Add mapPartitionsWithIndex for RDDBarrier.
### Why are the changes needed?
There is only one method in `RDDBarrier`. We often use the partition index as a label for the current partition. We need to get the index from `TaskContext` index in the method of `mapPartitions` which is not convenient.
### Does this PR introduce any user-facing change?
No
### How was this patch tested?
New UT.
Closes#26148 from ConeyLiu/barrier-index.
Authored-by: Xianyang Liu <xianyang.liu@intel.com>
Signed-off-by: Xingbo Jiang <xingbo.jiang@databricks.com>
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