Be able to know the percentage of resources used

Hello,

We want to be able to know if we need to add a new nomad client to handle our tasks or if we have too many nomad client for our load. For that, it could be useful to know how our clients are used (could be related with https://github.com/hashicorp/nomad/issues/2872). Today, we're able to know how our client is used via the `Resource Utilization` graph on each client, but instead of displaying the hardware limit, displaying the nomad's locked resources could be a good metric to estimate our needs.

Thanks

Start by reviewing the client Resource Utilization graph and the related issue #2872. Define how Nomad-locked resources should be measured against client capacity, then update the utilization view to expose the percentage needed to assess client capacity; verify the displayed metric against representative client workloads.

Written by the indexing model from the issue text.