Sparse Ops: Indexing with slice

## 🔨Work Item

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Project tracker: https://github.com/orgs/dmlc/projects/2

## Description
Indexing:
- A[i] or A[I] or A[I, :], row slicing, return sliced submatrix (sparse)
- A[:, j] or A[:, J], column slicing, return sliced submatrix (sparse)

## Depending work items or issues