Sub-resources in a toolbox

[kamil-mrzyglod]

Currently resourceTemplateProvider class contains only "main" resources. If you go to https://docs.microsoft.com/en-us/azure/templates/ you can see, that some components(like APIM) provide additional items like Authorization Servers or Backends. The goal is to add those as sub-resources(you can display them next to the base resource with the same icon).