add features endpoint for zos3 and zos4

[ashraffouda]

we need an endpoint that gets the supported features for zos node hence we have two different version now 3 and 4 and each one has its own workload types so we need this for dashboard for example to determine which types of workloads are valid for the node we are deploying on
something like the types here https://github.com/threefoldtech/zos/blob/main/pkg/gridtypes/zos/types.go#L10
the endpoint should return the supported types for workload names