tests: testcase to reproduce a variety of IO workloads

Mainly created to be used as a tool that reproduces specific workloads,
so allowing us to understand how underlying components are performing,
e.g. Adjustable Replacement Cache (ARC) from ZFS.

Reviewed-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>