Support referening outputs of resources from another env/project

[gitlawr]

Is your enhancement related to a problem? Please describe.
Users may manage the whole stack separately. For example,

• Manages network, security in project A
• Manage compute, filestore in project B

When we want to use a network output like vpc id in project B, there are following ways at the moment:

1. Set a static variable in project B.
2. Create a resource(static or using data sources) that has the vpc id output.

Solution 1 does not adapt to changes.
Solution 2 requires dedicated template for each case.

Describe the solution you'd like
Be able to create a resource in project B that references resource in project A and has corresponding outputs.

Additional context
Permission boudary between projects need to be properly considered.