Make it easier to work across all subscriptions a logged in user has access to under the user context

With having more than a small handful of subscriptions you soon have requirements to be able to work across all of them at ease. In the portal we are able to just see all things and not have to log into the subscription to be able to work with it.

Can the login/subscription management be overhauled to be based in the same manner as the portal as per #6549 when you have multiple subscriptions changing subscription context is not only time consuming but adds excess required code and looping within Subscriptions to be able to do some of the same tasks that you can do in the Portal.

Ideally using a context that has access to 2+ subscriptions should be able to call back all resources in those subsciptions without needing to explictly change the subscription individually.

However there should be logic implemented that would allow to be able to choose subscriptions to include/exclude under a context, something that I can manage to do very easily in the portal by choosing which subscriptions I want to query against and which ones I don't want to. This could be inplemented simple `-ExcludeSubscription` or `-IncludeSubcription` parameter.