[gp cli] gp command to print/show workspace class

[csweichel]

Is your feature request related to a problem? Please describe

We recently added an environment variable which carries the name of the workspace class a workspace is running on.

Describe the behaviour you'd like

Environment variables are not always stable - and we are trying to educate folks to not rely on them. Instead, we should plug this into the supervisor info endpoint, and add a gp command to access it.

[akosyakov]

I think the logical place will be gp top. It should show workspace class, its configuration for CPU and MEMORY, usage, and provide hints to upgrade if necessary.

To consume programatically we can provide an option like gp top --json.