Provide a means to show resource usage at the cluster level and resource pool level

[huib-portainer]

Is your feature request related to a problem? Please describe.
Right now, what we can see in the Resource Pool resource allocation and Cluster usage line graphs are whats actually ASSIGNED to applications.

Using the metrics API, we should be able to display a different colour bar for what is actually used.

This is an important feature as it allows the admin to see who is over-sizing their application allocations, as a way to encourage 'right-sizing" of allocations.

Its feasible a user would request 8GB of RAM for their MYSQL instance, only to have it use less than 1GB, with the rest being wasted as its reserved for exclusive use.

Describe the solution you'd like
In order to use this feature, the administrator user must turn on features using metrics server:

Show the resource usage in the resource reservation and usage panel:

Show the resource reservation and usage on the node level:

In the namespace show the resource reservation and usage at the namespace level: