[FEA] write a grep utility with cuDF

**Is your feature request related to a problem? Please describe.**
Regex features are available in cudf string APIs and nvtext APIs.
`grep` is widely used utility. It would cool to try creating `cudfgrep` with cudf/nvtext and document the throughput.

**Describe the solution you'd like**
Create `cudfgrep` utility in our python codebase or a C++ example with libcudf APIs.

**Additional context**
Benchmark it without GDS (most common usecase).
Benchmark on GPU in PCIE, and on Grace systems with fast C2C.