Have option to create Instance at point of creating a Pipeline Stage

### Description

> this feature was noted in a call with @biancode where he expected to be able to go via a Pipeline to create the Instances, rather than having to create them upfront

On the "Add Stage" screen, currently, users must assign a pre-existing Instance. There are two implementation stages to this:

1. Provide a shortcut/button to the "Add Instance" screen from the "Add Stage" if there are no Instances available
2. Integrate the workflow for creating an Instance _and_ a stage into the same view in some fashion.

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate