Connect to pre-provisioned stateful resources

Overview of roadmap item

The Radius vision includes the capability to connect to existing stateful resources (e.g. database, message queue) that were previously provisioned and existed outside of the scope of the Radius application, without affecting the data or state stored within those pre-provisioned resources. The most immediately prioritized work is to enable Radius to connect to such existing pre-provisioned resources using Recipes.

As a developer, I say what's required in my app, so I include the resources that I need and those can include external dependencies that are managed by other people. In some of the environments that I deploy to, those environments are going to be created dynamically in some of the environments that I deploy to, they might already exist because it's a database and people care about their existing data. And as a developer, I don't have to know which one it is, it's not a not my concern how that infrastructure is being managed and so some piece of the system has to provide that capability.

Related issues

### Related issues
- [ ] https://github.com/radius-project/radius/issues/6960
- [ ] https://github.com/radius-project/radius/issues/5497

Additional context

Start with this roadmap item and read related issues 6960 and 5497 to identify the implementation scope and current direction. Done means Radius can use Recipes to connect applications to existing stateful resources without changing the data or state in those resources.