use sets instead of lists in terraform schema

[mariobassem]

currently, lists are used in the provider's schema. any change to the order of the workloads in lists will result in unexpected behavior on the grid.

Instead, sets should be used to uniquely identify workloads not just by their place in a list.

[ashraffouda]

tried it with sets, it gave a weird behavior if for example have a 2 vms and modified one of them if shows that 4vms modified and need to deploy them, so we instead will use nestedMap feature in the new terraform framework, but this requires a lots of modifications to the current provider