external resource role assignment scope

This PR closes #1012

The original ask focused on removing the version requirement, but that is a huge and orthogonal change to the latter point that implicitly created dependency is actually a blocker.

The changes in this PR are as follows:

Allows creating scopes for resources Farmer doesn't manage.

I have read the contributing guidelines and have completed the following:

[x] Tested my code end-to-end against a live Azure subscription.
[ ] Updated the documentation in the docs folder for the affected changes.
[x] Written unit tests against the modified code that I have made.
[x] Updated the release notes with a new entry for this PR.
[x] Checked the coding standards outlined in the contributions guide and ensured my code adheres to them.

If I haven't completed any of the tasks above, I include the reasons why here: Role assignments have no docs.

Below is a minimal example configuration that includes the new features, which can be used to deploy to Azure:

                let actual : IArmResource = 
                    { Name = ResourceName "assignment"
                      RoleDefinitionId = Roles.Contributor
                      PrincipalId = ArmExpression.create "1" |> PrincipalId
                      PrincipalType = PrincipalType.User
                      Scope = privateClouds.resourceId "mySDDC" |> UnmanagedResource 
                      Dependencies = Set.empty }

CompositionalIT / farmer

external resource role assignment scope #1023