Allow use of the interactive subscription selector for selecting amongst already logged in accounts

[maskati]

Related command
az account set

Is your feature request related to a problem? Please describe.
The new SubscriptionSelector is useful when selecting amongst a list of subscriptions in interactive scenarios. Unfortunately it is only usable as part of the az login experience.

Describe the solution you'd like
Support the interactive subscription selector amongst existing logged in accounts e.g. az account set --interactive.

[yonzhan]

Thank you for opening this issue, we will look into it.