Add pool-specific scheduler config. This allows you to configure Fenzo settings per pool, instead of globally. Mainly, this change was introduced to allow us to configure a different scheduler from Fenzo (e.g. Kubernetes) for pools in the future.
The new pool-specific scheduler config is routed into the new pool handler factory, although it currently only supports the existing Fenzo scheduler.
Modify main function and unit tests to handle the new config.
Changes proposed in this PR
Why are we making these changes?