Possibility to import a reusable test, into a reusable test

Reusable tests are currently 1-level deep. It would be helpful to increase that limitation in order to support more advanced flows.

For example:
Test 1: I can login

Test 2: I can create a test

→ uses test 1 + custom logic

Test 3: I can run a test
→ uses test 1 + test 2 + custom logic