Optimize where_index_op(prefix sum) (#30601)
Optimize where_index_op(prefix sum) (#30601)

* new optimize for where_index_op with prefix sum version.

* write a scan prefix sum kernel with stream for where index op.

* optimize where_index by using cub::DeviceScan::InclusiveSum instead of imperfect self-kernel.

* remove CheckTrue struct and rename stide_array for readable.

* optimize variable name for readable.

* optimize function name and annotation.
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