Introduces collective overhead with the sends/receives and other
The changes made in model-net-mpi-replay.c includes:
- Introducing collective overhead with the sends/receives.
- Adding different background traffic pattern: all-to-all, 2D stencil, and nearest neighbor. The reverse handler might need to be fixed for optimistic mode.
- Modifying output of collective stats for collective validation study, the reverse handler is on to-do list.